Java-Codility-Challenges

# big-o-performance A simple html app to demonstrate performance costs of data structures. - Clone the project - Navigate to the root of the project in a termina or command prompt - Run 'npm install' - Run 'npm start' - Go to the URL specified in the terminal or command prompt to try out the app. # This app was created from the Create React App NPM. Below are instructions from that project. Below you will find some information on how to perform common tasks. You can find the most recent version of this guide [here](https://github.com/facebookincubator/create-react-app/blob/master/template/README.md). ## Table of Contents - [Updating to New Releases](#updating-to-new-releases) - [Sending Feedback](#sending-feedback) - [Folder Structure](#folder-structure) - [Available Scripts](#available-scripts) - [npm start](#npm-start) - [npm run build](#npm-run-build) - [npm run eject](#npm-run-eject) - [Displaying Lint Output in the Editor](#displaying-lint-output-in-the-editor) - [Installing a Dependency](#installing-a-dependency) - [Importing a Component](#importing-a-component) - [Adding a Stylesheet](#adding-a-stylesheet) - [Post-Processing CSS](#post-processing-css) - [Adding Images and Fonts](#adding-images-and-fonts) - [Adding Bootstrap](#adding-bootstrap) - [Adding Flow](#adding-flow) - [Adding Custom Environment Variables](#adding-custom-environment-variables) - [Integrating with a Node Backend](#integrating-with-a-node-backend) - [Proxying API Requests in Development](#proxying-api-requests-in-development) - [Deployment](#deployment) - [Now](#now) - [Heroku](#heroku) - [Surge](#surge) - [GitHub Pages](#github-pages) - [Something Missing?](#something-missing) ## Updating to New Releases Create React App is divided into two packages: * `create-react-app` is a global command-line utility that you use to create new projects. * `react-scripts` is a development dependency in the generated projects (including this one). You almost never need to update `create-react-app` itself: it’s delegates all the setup to `react-scripts`. When you run `create-react-app`, it always creates the project with the latest version of `react-scripts` so you’ll get all the new features and improvements in newly created apps automatically. To update an existing project to a new version of `react-scripts`, [open the changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md), find the version you’re currently on (check `package.json` in this folder if you’re not sure), and apply the migration instructions for the newer versions. In most cases bumping the `react-scripts` version in `package.json` and running `npm install` in this folder should be enough, but it’s good to consult the [changelog](https://github.com/facebookincubator/create-react-app/blob/master/CHANGELOG.md) for potential breaking changes. We commit to keeping the breaking changes minimal so you can upgrade `react-scripts` painlessly. ## Sending Feedback We are always open to [your feedback](https://github.com/facebookincubator/create-react-app/issues). ## Folder Structure After creation, your project should look like this: ``` my-app/ README.md index.html favicon.ico node_modules/ package.json src/ App.css App.js index.css index.js logo.svg ``` For the project to build, **these files must exist with exact filenames**: * `index.html` is the page template; * `favicon.ico` is the icon you see in the browser tab; * `src/index.js` is the JavaScript entry point. You can delete or rename the other files. You may create subdirectories inside `src`. For faster rebuilds, only files inside `src` are processed by Webpack. You need to **put any JS and CSS files inside `src`**, or Webpack won’t see them. You can, however, create more top-level directories. They will not be included in the production build so you can use them for things like documentation. ## Available Scripts In the project directory, you can run: ### `npm start` Runs the app in the development mode.<br> Open [http://localhost:3000](http://localhost:3000) to view it in the browser. The page will reload if you make edits.<br> You will also see any lint errors in the console. ### `npm run build` Builds the app for production to the `build` folder.<br> It correctly bundles React in production mode and optimizes the build for the best performance. The build is minified and the filenames include the hashes.<br> Your app is ready to be deployed! ### `npm run eject` **Note: this is a one-way operation. Once you `eject`, you can’t go back!** If you aren’t satisfied with the build tool and configuration choices, you can `eject` at any time. This command will remove the single build dependency from your project. Instead, it will copy all the configuration files and the transitive dependencies (Webpack, Babel, ESLint, etc) right into your project so you have full control over them. All of the commands except `eject` will still work, but they will point to the copied scripts so you can tweak them. At this point you’re on your own. You don’t have to ever use `eject`. The curated feature set is suitable for small and middle deployments, and you shouldn’t feel obligated to use this feature. However we understand that this tool wouldn’t be useful if you couldn’t customize it when you are ready for it. ## Displaying Lint Output in the Editor >Note: this feature is available with `react-scripts@0.2.0` and higher. Some editors, including Sublime Text, Atom, and Visual Studio Code, provide plugins for ESLint. They are not required for linting. You should see the linter output right in your terminal as well as the browser console. However, if you prefer the lint results to appear right in your editor, there are some extra steps you can do. You would need to install an ESLint plugin for your editor first. >**A note for Atom `linter-eslint` users** >If you are using the Atom `linter-eslint` plugin, make sure that **Use global ESLint installation** option is checked: ><img src="http://i.imgur.com/yVNNHJM.png" width="300"> Then make sure `package.json` of your project ends with this block: ```js { // ... "eslintConfig": { "extends": "./node_modules/react-scripts/config/eslint.js" } } ``` Projects generated with `react-scripts@0.2.0` and higher should already have it. If you don’t need ESLint integration with your editor, you can safely delete those three lines from your `package.json`. Finally, you will need to install some packages *globally*: ```sh npm install -g eslint babel-eslint eslint-plugin-react eslint-plugin-import eslint-plugin-jsx-a11y eslint-plugin-flowtype ``` We recognize that this is suboptimal, but it is currently required due to the way we hide the ESLint dependency. The ESLint team is already [working on a solution to this](https://github.com/eslint/eslint/issues/3458) so this may become unnecessary in a couple of months. ## Installing a Dependency The generated project includes React and ReactDOM as dependencies. It also includes a set of scripts used by Create React App as a development dependency. You may install other dependencies (for example, React Router) with `npm`: ``` npm install --save <library-name> ``` ## Importing a Component This project setup supports ES6 modules thanks to Babel. While you can still use `require()` and `module.exports`, we encourage you to use [`import` and `export`](http://exploringjs.com/es6/ch_modules.html) instead. For example: ### `Button.js` ```js import React, { Component } from 'react'; class Button extends Component { render() { // ... } } export default Button; // Don’t forget to use export default! ``` ### `DangerButton.js` ```js import React, { Component } from 'react'; import Button from './Button'; // Import a component from another file class DangerButton extends Component { render() { return <Button color="red" />; } } export default DangerButton; ``` Be aware of the [difference between default and named exports](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281). It is a common source of mistakes. We suggest that you stick to using default imports and exports when a module only exports a single thing (for example, a component). That’s what you get when you use `export default Button` and `import Button from './Button'`. Named exports are useful for utility modules that export several functions. A module may have at most one default export and as many named exports as you like. Learn more about ES6 modules: * [When to use the curly braces?](http://stackoverflow.com/questions/36795819/react-native-es-6-when-should-i-use-curly-braces-for-import/36796281#36796281) * [Exploring ES6: Modules](http://exploringjs.com/es6/ch_modules.html) * [Understanding ES6: Modules](https://leanpub.com/understandinges6/read#leanpub-auto-encapsulating-code-with-modules) ## Adding a Stylesheet This project setup uses [Webpack](https://webpack.github.io/) for handling all assets. Webpack offers a custom way of “extending” the concept of `import` beyond JavaScript. To express that a JavaScript file depends on a CSS file, you need to **import the CSS from the JavaScript file**: ### `Button.css` ```css .Button { padding: 20px; } ``` ### `Button.js` ```js import React, { Component } from 'react'; import './Button.css'; // Tell Webpack that Button.js uses these styles class Button extends Component { render() { // You can use them as regular CSS styles return <div className="Button" />; } } ``` **This is not required for React** but many people find this feature convenient. You can read about the benefits of this approach [here](https://medium.com/seek-ui-engineering/block-element-modifying-your-javascript-components-d7f99fcab52b). However you should be aware that this makes your code less portable to other build tools and environments than Webpack. In development, expressing dependencies this way allows your styles to be reloaded on the fly as you edit them. In production, all CSS files will be concatenated into a single minified `.css` file in the build output. If you are concerned about using Webpack-specific semantics, you can put all your CSS right into `src/index.css`. It would still be imported from `src/index.js`, but you could always remove that import if you later migrate to a different build tool. ## Post-Processing CSS This project setup minifies your CSS and adds vendor prefixes to it automatically through [Autoprefixer](https://github.com/postcss/autoprefixer) so you don’t need to worry about it. For example, this: ```css .App { display: flex; flex-direction: row; align-items: center; } ``` becomes this: ```css .App { display: -webkit-box; display: -ms-flexbox; display: flex; -webkit-box-orient: horizontal; -webkit-box-direction: normal; -ms-flex-direction: row; flex-direction: row; -webkit-box-align: center; -ms-flex-align: center; align-items: center; } ``` There is currently no support for preprocessors such as Less, or for sharing variables across CSS files. ## Adding Images and Fonts With Webpack, using static assets like images and fonts works similarly to CSS. You can **`import` an image right in a JavaScript module**. This tells Webpack to include that image in the bundle. Unlike CSS imports, importing an image or a font gives you a string value. This value is the final image path you can reference in your code. Here is an example: ```js import React from 'react'; import logo from './logo.png'; // Tell Webpack this JS file uses this image console.log(logo); // /logo.84287d09.png function Header() { // Import result is the URL of your image return <img src={logo} alt="Logo" />; } export default function Header; ``` This works in CSS too: ```css .Logo { background-image: url(./logo.png); } ``` Webpack finds all relative module references in CSS (they start with `./`) and replaces them with the final paths from the compiled bundle. If you make a typo or accidentally delete an important file, you will see a compilation error, just like when you import a non-existent JavaScript module. The final filenames in the compiled bundle are generated by Webpack from content hashes. If the file content changes in the future, Webpack will give it a different name in production so you don’t need to worry about long-term caching of assets. Please be advised that this is also a custom feature of Webpack. **It is not required for React** but many people enjoy it (and React Native uses a similar mechanism for images). However it may not be portable to some other environments, such as Node.js and Browserify. If you prefer to reference static assets in a more traditional way outside the module system, please let us know [in this issue](https://github.com/facebookincubator/create-react-app/issues/28), and we will consider support for this. ## Adding Bootstrap You don’t have to use [React Bootstrap](https://react-bootstrap.github.io) together with React but it is a popular library for integrating Bootstrap with React apps. If you need it, you can integrate it with Create React App by following these steps: Install React Bootstrap and Bootstrap from NPM. React Bootstrap does not include Bootstrap CSS so this needs to be installed as well: ``` npm install react-bootstrap --save npm install bootstrap@3 --save ``` Import Bootstrap CSS and optionally Bootstrap theme CSS in the ```src/index.js``` file: ```js import 'bootstrap/dist/css/bootstrap.css'; import 'bootstrap/dist/css/bootstrap-theme.css'; ``` Import required React Bootstrap components within ```src/App.js``` file or your custom component files: ```js import { Navbar, Jumbotron, Button } from 'react-bootstrap'; ``` Now you are ready to use the imported React Bootstrap components within your component hierarchy defined in the render method. Here is an example [`App.js`](https://gist.githubusercontent.com/gaearon/85d8c067f6af1e56277c82d19fd4da7b/raw/6158dd991b67284e9fc8d70b9d973efe87659d72/App.js) redone using React Bootstrap. ## Adding Flow Flow typing is currently [not supported out of the box](https://github.com/facebookincubator/create-react-app/issues/72) with the default `.flowconfig` generated by Flow. If you run it, you might get errors like this: ```js node_modules/fbjs/lib/Deferred.js.flow:60 60: Promise.prototype.done.apply(this._promise, arguments); ^^^^ property `done`. Property not found in 495: declare class Promise<+R> { ^ Promise. See lib: /private/tmp/flow/flowlib_34952d31/core.js:495 node_modules/fbjs/lib/shallowEqual.js.flow:29 29: return x !== 0 || 1 / (x: $FlowIssue) === 1 / (y: $FlowIssue); ^^^^^^^^^^ identifier `$FlowIssue`. Could not resolve name src/App.js:3 3: import logo from './logo.svg'; ^^^^^^^^^^^^ ./logo.svg. Required module not found src/App.js:4 4: import './App.css'; ^^^^^^^^^^^ ./App.css. Required module not found src/index.js:5 5: import './index.css'; ^^^^^^^^^^^^^ ./index.css. Required module not found ``` To fix this, change your `.flowconfig` to look like this: ```ini [libs] ./node_modules/fbjs/flow/lib [options] esproposal.class_static_fields=enable esproposal.class_instance_fields=enable module.name_mapper='^\(.*\)\.css$' -> 'react-scripts/config/flow/css' module.name_mapper='^\(.*\)\.\(jpg\|png\|gif\|eot\|otf\|webp\|svg\|ttf\|woff\|woff2\|mp4\|webm\)$' -> 'react-scripts/config/flow/file' suppress_type=$FlowIssue suppress_type=$FlowFixMe ``` Re-run flow, and you shouldn’t get any extra issues. If you later `eject`, you’ll need to replace `react-scripts` references with the `<PROJECT_ROOT>` placeholder, for example: ```ini module.name_mapper='^\(.*\)\.css$' -> '<PROJECT_ROOT>/config/flow/css' module.name_mapper='^\(.*\)\.\(jpg\|png\|gif\|eot\|otf\|webp\|svg\|ttf\|woff\|woff2\|mp4\|webm\)$' -> '<PROJECT_ROOT>/config/flow/file' ``` We will consider integrating more tightly with Flow in the future so that you don’t have to do this. ## Adding Custom Environment Variables >Note: this feature is available with `react-scripts@0.2.3` and higher. Your project can consume variables declared in your environment as if they were declared locally in your JS files. By default you will have `NODE_ENV` defined for you, and any other environment variables starting with `REACT_APP_`. These environment variables will be defined for you on `process.env`. For example, having an environment variable named `REACT_APP_SECRET_CODE` will be exposed in your JS as `process.env.REACT_APP_SECRET_CODE`, in addition to `process.env.NODE_ENV`. These environment variables can be useful for displaying information conditionally based on where the project is deployed or consuming sensitive data that lives outside of version control. First, you need to have environment variables defined, which can vary between OSes. For example, let's say you wanted to consume a secret defined in the environment inside a `<form>`: ```jsx render() { return ( <div> <small>You are running this application in <b>{process.env.NODE_ENV}</b> mode.</small> <form> <input type="hidden" defaultValue={process.env.REACT_APP_SECRET_CODE} /> </form> </div> ); } ``` The above form is looking for a variable called `REACT_APP_SECRET_CODE` from the environment. In order to consume this value, we need to have it defined in the environment: ### Windows (cmd.exe) ```cmd set REACT_APP_SECRET_CODE=abcdef&&npm start ``` (Note: the lack of whitespace is intentional.) ### Linux, OS X (Bash) ```bash REACT_APP_SECRET_CODE=abcdef npm start ``` > Note: Defining environment variables in this manner is temporary for the life of the shell session. Setting permanent environment variables is outside the scope of these docs. With our environment variable defined, we start the app and consume the values. Remember that the `NODE_ENV` variable will be set for you automatically. When you load the app in the browser and inspect the `<input>`, you will see its value set to `abcdef`, and the bold text will show the environment provided when using `npm start`: ```html <div> <small>You are running this application in <b>development</b> mode.</small> <form> <input type="hidden" value="abcdef" /> </form> </div> ``` Having access to the `NODE_ENV` is also useful for performing actions conditionally: ```js if (process.env.NODE_ENV !== 'production') { analytics.disable(); } ``` ## Integrating with a Node Backend Check out [this tutorial](https://www.fullstackreact.com/articles/using-create-react-app-with-a-server/) for instructions on integrating an app with a Node backend running on another port, and using `fetch()` to access it. You can find the companion GitHub repository [here](https://github.com/fullstackreact/food-lookup-demo). ## Proxying API Requests in Development >Note: this feature is available with `react-scripts@0.2.3` and higher. People often serve the front-end React app from the same host and port as their backend implementation. For example, a production setup might look like this after the app is deployed: ``` / - static server returns index.html with React app /todos - static server returns index.html with React app /api/todos - server handles any /api/* requests using the backend implementation ``` Such setup is **not** required. However, if you **do** have a setup like this, it is convenient to write requests like `fetch('/api/todos')` without worrying about redirecting them to another host or port during development. To tell the development server to proxy any unknown requests to your API server in development, add a `proxy` field to your `package.json`, for example: ```js "proxy": "http://localhost:4000", ``` This way, when you `fetch('/api/todos')` in development, the development server will recognize that it’s not a static asset, and will proxy your request to `http://localhost:4000/api/todos` as a fallback. Conveniently, this avoids [CORS issues](http://stackoverflow.com/questions/21854516/understanding-ajax-cors-and-security-considerations) and error messages like this in development: ``` Fetch API cannot load http://localhost:4000/api/todos. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled. ``` Keep in mind that `proxy` only has effect in development (with `npm start`), and it is up to you to ensure that URLs like `/api/todos` point to the right thing in production. You don’t have to use the `/api` prefix. Any unrecognized request will be redirected to the specified `proxy`. Currently the `proxy` option only handles HTTP requests, and it won’t proxy WebSocket connections. If the `proxy` option is **not** flexible enough for you, alternatively you can: * Enable CORS on your server ([here’s how to do it for Express](http://enable-cors.org/server_expressjs.html)). * Use [environment variables](#adding-custom-environment-variables) to inject the right server host and port into your app. ## Deployment By default, Create React App produces a build assuming your app is hosted at the server root. To override this, specify the `homepage` in your `package.json`, for example: ```js "homepage": "http://mywebsite.com/relativepath", ``` This will let Create React App correctly infer the root path to use in the generated HTML file. ### Now See [this example](https://github.com/xkawi/create-react-app-now) for a zero-configuration single-command deployment with [now](https://zeit.co/now). ### Heroku Use the [Heroku Buildpack for Create React App](https://github.com/mars/create-react-app-buildpack). You can find instructions in [Deploying React with Zero Configuration](https://blog.heroku.com/deploying-react-with-zero-configuration). ### Surge Install the Surge CLI if you haven't already by running `npm install -g surge`. Run the `surge` command and log in you or create a new account. You just need to specify the *build* folder and your custom domain, and you are done. ```sh email: email@domain.com password: ******** project path: /path/to/project/build size: 7 files, 1.8 MB domain: create-react-app.surge.sh upload: [====================] 100%, eta: 0.0s propagate on CDN: [====================] 100% plan: Free users: email@domain.com IP Address: X.X.X.X Success! Project is published and running at create-react-app.surge.sh ``` Note that in order to support routers that use html5 `pushState` API, you may want to rename the `index.html` in your build folder to `200.html` before deploying to Surge. This [ensures that every URL falls back to that file](https://surge.sh/help/adding-a-200-page-for-client-side-routing). ### GitHub Pages >Note: this feature is available with `react-scripts@0.2.0` and higher. Open your `package.json` and add a `homepage` field: ```js "homepage": "http://myusername.github.io/my-app", ``` **The above step is important!** Create React App uses the `homepage` field to determine the root URL in the built HTML file. Now, whenever you run `npm run build`, you will see a cheat sheet with a sequence of commands to deploy to GitHub pages: ```sh git commit -am "Save local changes" git checkout -B gh-pages git add -f build git commit -am "Rebuild website" git filter-branch -f --prune-empty --subdirectory-filter build git push -f origin gh-pages git checkout - ``` You may copy and paste them, or put them into a custom shell script. You may also customize them for another hosting provider. Note that GitHub Pages doesn't support routers that use the HTML5 `pushState` history API under the hood (for example, React Router using `browserHistory`). This is because when there is a fresh page load for a url like `http://user.github.io/todomvc/todos/42`, where `/todos/42` is a frontend route, the GitHub Pages server returns 404 because it knows nothing of `/todos/42`. If you want to add a router to a project hosted on GitHub Pages, here are a couple of solutions: * You could switch from using HTML5 history API to routing with hashes. If you use React Router, you can switch to `hashHistory` for this effect, but the URL will be longer and more verbose (for example, `http://user.github.io/todomvc/#/todos/42?_k=yknaj`). [Read more](https://github.com/reactjs/react-router/blob/master/docs/guides/Histories.md#histories) about different history implementations in React Router. * Alternatively, you can use a trick to teach GitHub Pages to handle 404 by redirecting to your `index.html` page with a special redirect parameter. You would need to add a `404.html` file with the redirection code to the `build` folder before deploying your project, and you’ll need to add code handling the redirect parameter to `index.html`. You can find a detailed explanation of this technique [in this guide](https://github.com/rafrex/spa-github-pages). ## Something Missing? If you have ideas for more “How To” recipes that should be on this page, [let us know](https://github.com/facebookincubator/create-react-app/issues) or [contribute some!](https://github.com/facebookincubator/create-react-app/edit/master/template/README.md)

In Agriculture Price Monitioring , I have used data provided by open government site data.gov.in, which updates prices of market daily . Working Interface Details: We have provided user choice to see current market prices based on two choices: market wise or commodity wise use increase assesibility options. Market wise: User have to provide State,District and Market name and then select market wise button. Then user will be shown the prices of all the commodities present in the market in graphical format, so that he can analyse the rates on one scale. This feature is mostly helpful for a regular buyer to decide the choice of commodity to buy. He is also given feature to download the data in a tabular format(csv) for accurate analysis. Commodity Wise: User have to provide State,District and Commodity name and then select Commodity wise button. Then user will be shown the prices of all the markets present in the region with the commodity in graphical format, so that he can analyse the cheapest commodity rate. This feature is mostly helpful for wholesale buyers. He is also given feature to download the data in a tabular format(csv) for accurate analysis. On the first activity user is also given forecasting choice. It can be used to forecast the wholesale prices of various commodities at some later year. Regression techniques on timeseries data is used to predict future prices. Select the type of item and click link for future predictions. There are 3 java files Forecasts, DisplayGraphs, DisplayGraphs2 ..... Please change the localhost "server_name" at time of testing as the server name changes each time a new server is made. Things Used: We have used pandas , numpy , scikit learn , seaborn and matplotlib libraries for the same . The dataset is thoroughly analysed using different function available in pandas in my .iPynb file . Not just in-built functions are used but also many user made functions are made to make the working smooth . Various graphs like pointplot , heat-map , barplot , kdeplot , distplot, pairplot , stripplot , jointplot, regplot , etc are made and also deployed on the android app as well . To integrate the android app and machine learning analysis outputs , we have used Flask to host our laptop as the server . We have a separate file for the Flask as server.py . Where all the the necessary stuff of clint request and server response have been dealt with . We have used npm package ngrok for tunneling purpose and hosting . A different .iPynb file is used for the time series predictions using regression algorithms and would send the csv file of prediction along with the graph to the andoid app when given a request .

This is an open source codes for you of URI online Judge. Here, I've added some URI problems solution in C, C++ and in Java languages.You can use these URI Online judge solutions in your coding time on URI.. As a programmer, I first suggest you to try these code first. It will be the best if you do your own code. And obviously solving one problem more than 2-3 days of URI online judge not a good idea at all. So here, You can get all the URI Online Judge Problems Solution and solve URI Problems easily all of the URI Problems. I may be add one problems solution in different languages(C, C++, Java). From them, C++/cpp is the best solution, Promise. You can get any individual URI online Judge Problem's Solution at https://urisolve.blogspot.com Contact with me at my mail for any problem : manirujjamanakash@gmail.com

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</div> <br> <div class="w3-example"> <h3>Example</h3> <p>A paragraph is marked up as follows:</p> <div class="w3-code notranslate htmlHigh"> <span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>p<span class="tagcolor" style="color:mediumblue">&gt;</span></span>This is some text in a paragraph.<span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/p<span class="tagcolor" style="color:mediumblue">&gt;</span></span> </div> <a target="_blank" href="tryit.asp?filename=tryhtml_paragraphs1" class="w3-btn w3-margin-bottom">Try it Yourself »</a> </div> <p>More "Try it Yourself" examples below.</p> <hr> <h2>Definition and Usage</h2> <p>The <code class="w3-codespan">&lt;p&gt;</code> tag defines a paragraph.</p> <p>Browsers automatically add a single blank line before and after each <code class="w3-codespan">&lt;p&gt;</code> element.</p> <p><strong>Tip:</strong> Use CSS to <a href="/html/html_css.asp">style paragraphs</a>.</p> <hr> <h2>Browser Support</h2> <table class="browserref notranslate"> <tbody><tr> <th style="width:20%;font-size:16px;text-align:left;">Element</th> <th style="width:16%;" class="bsChrome" title="Chrome"></th> <th style="width:16%;" class="bsEdge" title="Internet Explorer / Edge"></th> <th style="width:16%;" class="bsFirefox" title="Firefox"></th> <th style="width:16%;" class="bsSafari" title="Safari"></th> <th style="width:16%;" class="bsOpera" title="Opera"></th> </tr><tr> <td style="text-align:left;">&lt;p&gt;</td> <td>Yes</td> <td>Yes</td> <td>Yes</td> <td>Yes</td> <td>Yes</td> </tr> </tbody></table> <hr> <h2>Global Attributes</h2> <p>The <code class="w3-codespan">&lt;p&gt;</code> tag also supports the <a href="ref_standardattributes.asp">Global Attributes in HTML</a>.</p> <hr> <h2>Event Attributes</h2> <p>The <code class="w3-codespan">&lt;p&gt;</code> tag also supports the <a href="ref_eventattributes.asp">Event Attributes in HTML</a>.</p> <hr> <div id="midcontentadcontainer" style="overflow:auto;text-align:center"> <!-- MidContent --> <!-- <p class="adtext">Advertisement</p> --> <div id="adngin-mid_content-0" data-google-query-id="CKfs_8ueqvcCFXiOSwUd2fYBLg"><div id="sn_ad_label_adngin-mid_content-0" class="sn_ad_label" style="color:#000000;font-size:12px;margin:0;text-align:center;">ADVERTISEMENT</div><div id="google_ads_iframe_/22152718,16833175/sws-hb//w3schools.com//mid_content_1__container__" style="border: 0pt none; display: inline-block; width: 300px; height: 250px;"><iframe frameborder="0" src="https://56d0da6c34aaa471db22bb4266aac656.safeframe.googlesyndication.com/safeframe/1-0-38/html/container.html" id="google_ads_iframe_/22152718,16833175/sws-hb//w3schools.com//mid_content_1" title="3rd party ad content" name="" scrolling="no" marginwidth="0" marginheight="0" width="300" height="250" data-is-safeframe="true" sandbox="allow-forms allow-popups allow-popups-to-escape-sandbox allow-same-origin allow-scripts allow-top-navigation-by-user-activation" role="region" aria-label="Advertisement" tabindex="0" data-google-container-id="8" style="border: 0px; vertical-align: bottom;" data-load-complete="true"></iframe></div></div> </div> <hr> <h2>More Examples</h2> <div class="w3-example"> <h3>Example</h3> <p>Align text in a paragraph (with CSS):</p> <div class="w3-code notranslate htmlHigh"> <span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>p<span class="attributecolor" style="color:red"> style<span class="attributevaluecolor" style="color:mediumblue">="text-align:right"</span></span><span class="tagcolor" style="color:mediumblue">&gt;</span></span>This is some text in a paragraph.<span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/p<span class="tagcolor" style="color:mediumblue">&gt;</span></span> </div> <a target="_blank" href="tryit.asp?filename=tryhtml_p_align_css" class="w3-btn w3-margin-bottom">Try it Yourself »</a> </div> <div class="w3-example"> <h3>Example</h3> <p>Style paragraphs with CSS:</p> <div class="w3-code notranslate htmlHigh"> <span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>html<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>head<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>style<span class="tagcolor" style="color:mediumblue">&gt;</span></span><span class="cssselectorcolor" style="color:brown"><br>p <span class="cssdelimitercolor" style="color:black">{</span><span class="csspropertycolor" style="color:red"><br>&nbsp; color<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> navy<span class="cssdelimitercolor" style="color:black">;</span></span><br>&nbsp; text-indent<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> 30px<span class="cssdelimitercolor" style="color:black">;</span></span><br>&nbsp; text-transform<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> uppercase<span class="cssdelimitercolor" style="color:black">;</span></span><br></span><span class="cssdelimitercolor" style="color:black">}</span><br></span><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/style<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br> <span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/head<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>body<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br><br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>p<span class="tagcolor" style="color:mediumblue">&gt;</span></span>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.<span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/p<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br><br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/body<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/html<span class="tagcolor" style="color:mediumblue">&gt;</span></span> </div> <a target="_blank" href="tryit.asp?filename=tryhtml_p_style_css" class="w3-btn w3-margin-bottom">Try it Yourself »</a> </div> <div class="w3-example"> <h3>Example</h3> <p>&nbsp;More on paragraphs:</p> <div class="w3-code notranslate htmlHigh"> <span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>p<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br>This paragraph<br>contains a lot of lines<br>in the source code,<br> but the browser <br>ignores it.<br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/p<span class="tagcolor" style="color:mediumblue">&gt;</span></span> </div> <a target="_blank" href="tryit.asp?filename=tryhtml_paragraphs2" class="w3-btn w3-margin-bottom">Try it Yourself »</a> </div> <div class="w3-example"> <h3>Example</h3> <p>Poem problems in HTML:</p> <div class="w3-code notranslate htmlHigh"> <span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>p<span class="tagcolor" style="color:mediumblue">&gt;</span></span><br>My Bonnie lies over the ocean.<br>My Bonnie lies over the sea.<br>My Bonnie lies over the ocean.<br>Oh, bring back my Bonnie to me.<br><span class="tagnamecolor" style="color:brown"><span class="tagcolor" style="color:mediumblue">&lt;</span>/p<span class="tagcolor" style="color:mediumblue">&gt;</span></span> </div> <a target="_blank" href="tryit.asp?filename=tryhtml_poem" class="w3-btn w3-margin-bottom">Try it Yourself »</a> </div> <hr> <h2>Related Pages</h2> <p>HTML tutorial: <a href="/html/html_paragraphs.asp">HTML Paragraphs</a></p> <p>HTML DOM reference: <a href="/jsref/dom_obj_paragraph.asp">Paragraph Object</a></p> <hr> <h2>Default CSS Settings</h2> <p>Most browsers will display the <code class="w3-codespan">&lt;p&gt;</code> element with the following default values:</p> <div class="w3-example"> <h3>Example</h3> <div class="w3-code notranslate cssHigh"><span class="cssselectorcolor" style="color:brown"> p <span class="cssdelimitercolor" style="color:black">{</span><span class="csspropertycolor" style="color:red"><br>&nbsp; display<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> block<span class="cssdelimitercolor" style="color:black">;</span></span><br>&nbsp; margin-top<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> 1em<span class="cssdelimitercolor" style="color:black">;</span></span><br>&nbsp; margin-bottom<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> 1em<span class="cssdelimitercolor" style="color:black">;</span></span><br>&nbsp; margin-left<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> 0<span class="cssdelimitercolor" style="color:black">;</span></span><br>&nbsp;&nbsp;margin-right<span class="csspropertyvaluecolor" style="color:mediumblue"><span class="cssdelimitercolor" style="color:black">:</span> 0<span class="cssdelimitercolor" style="color:black">;</span></span><br></span><span class="cssdelimitercolor" style="color:black">}</span> 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Please Read Me First. This is a set of java file of my final version of electronic artifacts. This is a game to map my experience in Disney World, in Orlando during this spring break. However, because of my limited skills in computer science, I really have no idea how to simplify the process to run the game. Sorry for the inconvenience. In order to run the game, you may need to install JAVA. I hope the following links will help you.     http://www.oracle.com/technetwork/java/javase/downloads/index-jsp-138363.html#javasejdk
    http://www.cc.gatech.edu/~simpkins/teaching/gatech/cs1331/guides/install-java.html My main file is called Disney. You can call Disney in console to start the game. However, I failed to putting all the things inside Disney file. Therefore, you may also need to call AdventureLand, MainStreet, and FrontierLand to start other three games. I hope this will help you. Sorry again for the inconvenience. 1. the structure of my project My project only focused on my trip in Magic Kingdom, one part of Disney world in Orlando. It is a game which guides players to choose from six sub-games, which match six sections of the park, Main Street U.S.A, Tomorrowland, Adventureland, Frontierland, Fantasyland and Liberty Square. I chose one of the rides I took in each section which, from my perspective, shows what I found interesting in Disney world. I changed what I experienced in the park into a small computer game. I want to share my experience with others while they play my games. In the following part of self reflection, I explain the background, rules and other things about each game. For convenience of matching them, I use different color to mark different parts. I hope it will help readers a little bit when they are lost in my disordered reflections. 1. the hall of presidents - Liberty Square 2. Festivall parade - Fantasyland (I explain this one in the part of technology skill limitations) 3. Big Thunder Mountain Railroad - Frontierland 4.talking with Woody- Adventureland 5. Stitch Store - Tomorrowland 6. lunch time - Main Street USA 3. my reflection of the trip in Disney World from dream to reality When I exited Disney resort, I found a sign along the street welcomed people back to real world. Actually, when I was in Orlando, I couldn't believe as an adult, people can mess up fantasy world in the theme parks and the real world. Nevertheless, I felt I was still in fantasy world, when I dreamed twice that I fought for the key to open the door of future. As is known to all, while sleeping, people always dream about what people thinks in the daytime. Therefore, my dream shows that my mind still stayed in the world with Mickey and Donald. I believe that it is experiencing fantasy world which is the source of the greatest happiness people get from theme park. On the one hand, everybody has pressure in real life especially for adults. They can get out of pressure for a day trip in theme park. They can experience different lives here with cartoon characters. On the other hand, sometimes, it is a really hard task to fulfill some dreams, such as being a princess. However, in Disney world, you can dress up the same as Snow White, waiting for your prince; you can go to space by rocket; you can also travel all over the world in one day and enjoy the food of each country. These are all the magic of theme parks. Therefore, in my game, I learnt the way which Disney design their rides to focus on the background story of the game instead of the game itself. For example, there is a ride called Big Thunder Mountain Railroad, which streaks through a haunted gold-mining town aboard a rollicking runaway mine train. The views around the ride were like a gold mining town. There were tools for gold-mining around the railroad and the railroad looked like very old. In order to show riders that it was a haunted gold-mining town, the train always took a sudden turn or speed up quickly to scare people. I decided to name one of my game, which was inspired by this ride, the same name, Big Thunder Mountain Railroad. Instead of sitting inside the mine train to travel around the haunted town, mine was for users to use keyboard to control the train to travel around the gridding railroad. I place traps inside several parts of gridding to "scare" players, who cannot know where traps are until they get into them. If I know how to use animation, I will show scary pictures when players drive their train to the traps. Unlike the ride in Disney, my players can no longer travel once they encounter a trap because their train may have some problems to keep moving. Also, the main goal in the game is to find the gold. However, as we know, finding gold is really hard. Therefore, players must go to find Aladdin's Wonderful lamp where also places inside the gridding while players cannot see its exact place until they happen to drive inside the part where lamp is. Aladdin's Wonderful lamp will show players the map of the gold and when people get to the gold mine, they win. However, there is another limitation of the game. Haunted town is so dangerous during the night. Therefore, players only have 12 hours to finish the task. Train can drive one square in 20 min. Therefore, train can only move 36 times or they will also be caught by traps. In this game, I want to show audiences I have a background story like rides in Disney World. Players need to find the gold in a haunted gold-mining town. Also, in order to show the relationship with Disney, I use Aladdin's Wonderful Lamp as the guide for the players, which is a well known characters in Disney cartoon. I created another game, called talking with Woody to show the magic power of Disney characters. There are a lot of chances to meet Disney characters in Disney world. On the one hand, travelers, especially small kids, are really excited to meet the characters they watched on TV. I think some kids may believe they take pictures with real Mickey Mouse. On the hand, staffs in Disney who wear the costumes are really tired. It was hot in Orlando last week, but all costumes were very heavy. I was moved by the staffs inside Mickey. They also need to mimic the actions of characters and also need to show kindness and warmness to children. It seems like a really hard job. Therefore, I decide to show this part of Disney in my project as well. I decided to use Woody, a toy all the toys look up to. He is smart, kind and brave like a cowboy should be. He is more than a top, he is friend to everyone enjoying the movie Toy. In order to create an interactive game, I planned to ask players to guide Woody. Players need to call Woody before their instructions. For instance, if players say (actually players are typing) "Woody, please sit down", Woody will sit down (actually, there will be another line on the screen showing the same as players import). However, if players are rude and just say "sit down" without calling Woody, Woody won't act (actually there is just nothing showing up on the screen). great facilities to provide convenience to everyone The facilities to satisfy needs for special groups of people, like small kids or disabled people, are well developed. In the past in China, it seemed impossible for parents to take infants and small kids to travel. The road is not flat or wide enough for strollers or wheelchairs. However, in Disney world, everything seemed like well prepared for everyone to use. There are strollers rentals, and electric conveyance vehicles rentals, which are available to rent throughout Disney world. There are baby care center for mothers to feed, change and nurse little ones. There are locker rentals for storing personal items. There are also hearing disability services which have sign language interpretation to help disabled people to enjoy fantasy world. There are still a lot other convenient services in Disney world. I think the purpose of these services show the pursue of equality among everyone in the world. On the one hand, I am really touched by the availability of these services here. It seems Disney try its best to service everyone who have desire to experience fantasy land. On the other hand, in this way, Disney can attract more travelers in order to make more money in some ways. Also, in Disney, it seems like a tradition that there are stores at the exit of the famous rides. Somebody may think it is just a strategy to make people shopping a lot. However, I think it also provides some convenience that travelers can buy souvenirs where is memorable. For example, when I finished my trip in Escape Stitch, I entered a store with a lot of kinds of Stitch, like Stitch pillow, Stitch key chain and so on. I really want to buy something in order to remind me the wonderful feelings. Therefore, I showed my opinion inside my game as well. I wrote one part is for shopping. The items are different kinds of Stitch. My codes can act as a robot to help customers to shop in the store. There are a lot of restaurants in Disney. Maps of Disney are full of restaurants' name. The greatest things about the food are in Epcot, I experienced different counties in one day. I felt like I was in fast travel in different parts of the world and tasted their special food and snacks while I was on the way. I remembered I was still eating Japanese food when I was in "Mexico". It was a great experience. However, there were always a long waiting lines for the all restaurants. People needed to reserve a table a day before their trip and even they had the reservation, they still needed to wait for a long time. I think Disney may need some good ways to fix the problems of waiting for a long time. I have no idea of changing the situation of restaurants, but I think if there are robots to customers to order in fast food restaurant, it may help a lot. Thus, I have another code to customers to order in Plaza Restaurant. If this kind of robots can work in the real life, people can order by themselves and there will be more staffs available to prepare food. theme park uses interesting ways to teach knowledge of boring topics Theme part is also a great source of learning knowledge, especially for kids. They use Disney characters, interesting shows, or even games to teach useful things. The ways change the boring knowledge to interesting things, which always attract children's attention. The most amazing one was an interactive game in Epcot's Innoventions, called "where's the fire?", which teaches adults and children basic fire safety in a fun and entertaining way. About every five minutes, the players waiting in line are divided into two groups and move into the home's entry. Here, a host will explain the object of the game and lay out the rules. The scenario is this: you are on a mission to discover a number of fire hazards commonly found around the house. To do this, you move from room to room, looking for potential risks. To help in the task, each player is given a special "safely light" to help uncover lurking dangers. The rooms are large projection screens. When a hazard is discovered, all persons in the room must shine their safety light on the same spot. when they do, the hazard is rendered harmless and points are assigned. After playing in the game to find the hazardous things in the house, I learned a lot of safety tips. It is much easier to remember the tips I learned during the game than those I learned on textbook or internet. I believe kids will enjoy the games and learn from them as well. I also tried to show this reflection in my project. Thus, I planned to make a game, called the hall of presidents, which test people's knowledge of presidents in USA. However, I failed to achieve the goal of making it an entertaining game instead of a quiz. My game was still like a quiz. However, because it is the only code which can work well inside my big game. I decide to still hold the game for my projects in order to what my original ideas are. 4. technology skill limitations I feel terribly sorry for my limited skills in CS. It is my first time to learn JAVA this semester. I just begin to learn the core concepts of JAVA this month. When I choose to use java code for this project, I know I will face plentiful limitations and problems. Here I want to express my gratitude to Dr. Johnson, who encouraged me not to give up my ideas. To be honest, I have no idea of how to change a java code into a real game with animations. I know the background story of the game is more important for English course and pictures are the best way to show the background, but I have no idea to show all these things by JAVA coding. Therefore, I choose to use videos for my presentation. In this way, I can show my animation inside the videos while the code clue of my game is still composed by JAVA coding. Also, video gives me a lot of freedom when choose my contents for presentation. I can explain a lot details of my project clearly through videos. For example, I found the festival parade in the magic kingdom was great and I wanted to share the experience in my project by showing the pictures or videos. However, because of the technology limitations, I can only show the videos in my presentations. Also, I mistakenly deleted my videos which I shot on my trip Orlando, I can only share others' parade show...... Also, I want to apologize for the incompleteness of my game. I only dedicated to writing codes for Magic Kingdom, a part of my trip during spring break. Writing codes is a really time consuming task for me. In general, I need to spend more than eight hours to finish one project for my CS assignment this semester. While for this project, the final artifacts are composed of several parts of codes and in the end I need to write the father code in order to take care of my code family for spring break. Due to my limitation in writing codes, I can only finish one part of Disney world. However, I think my code shows all my reflections and perspectives during my trip, even though it looks like it only shows one part of my trip. The terrible mistake I made is that I found out the most of my codes I wrote had significant errors on Tuesday. I went to CS TA office for help, while the errors were still impossible to fix in order to achieve the goal I planned to get. Consequently, my game have to be separated into several parts. Instead of a big game having others as sub-games inside the big one, my final artifacts are composed by several small games. I need to start them one by one. It may cause some inconvenience for players to map their trip in Disney world.

 [](https://search.maven.org/search?q=g:net.openid%20appauth) [](http://javadoc.io/doc/net.openid/appauth) [](https://github.com/openid/AppAuth-Android/actions/workflows/build.yml) [](https://codecov.io/github/openid/AppAuth-Android?branch=master) AppAuth for Android is a client SDK for communicating with [OAuth 2.0](https://tools.ietf.org/html/rfc6749) and [OpenID Connect](http://openid.net/specs/openid-connect-core-1_0.html) providers. It strives to directly map the requests and responses of those specifications, while following the idiomatic style of the implementation language. In addition to mapping the raw protocol flows, convenience methods are available to assist with common tasks like performing an action with fresh tokens. The library follows the best practices set out in [RFC 8252 - OAuth 2.0 for Native Apps](https://tools.ietf.org/html/rfc8252), including using [Custom Tabs](https://developer.chrome.com/multidevice/android/customtabs) for authorization requests. For this reason, `WebView` is explicitly *not* supported due to usability and security reasons. The library also supports the [PKCE](https://tools.ietf.org/html/rfc7636) extension to OAuth which was created to secure authorization codes in public clients when custom URI scheme redirects are used. The library is friendly to other extensions (standard or otherwise) with the ability to handle additional parameters in all protocol requests and responses. A talk providing an overview of using the library for enterprise single sign-on (produced by Google) can be found here: [Enterprise SSO with Chrome Custom Tabs](https://www.youtube.com/watch?v=DdQTXrk6YTk). ## Download AppAuth for Android is available on [MavenCentral](https://search.maven.org/search?q=g:net.openid%20appauth) ```groovy implementation 'net.openid:appauth:<version>' ``` ## Requirements AppAuth supports Android API 16 (Jellybean) and above. Browsers which provide a custom tabs implementation are preferred by the library, but not required. Both Custom URI Schemes (all supported versions of Android) and App Links (Android M / API 23+) can be used with the library. In general, AppAuth can work with any Authorization Server (AS) that supports native apps as documented in [RFC 8252](https://tools.ietf.org/html/rfc8252), either through custom URI scheme redirects, or App Links. AS's that assume all clients are web-based or require clients to maintain confidentiality of the client secrets may not work well. ## Demo app A demo app is contained within this repository. For instructions on how to build and configure this app, see the [demo app readme](https://github.com/openid/AppAuth-Android/blob/master/app/README.md). ## Conceptual overview AppAuth encapsulates the authorization state of the user in the [net.openid.appauth.AuthState](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthState.java) class, and communicates with an authorization server through the use of the [net.openid.appauth.AuthorizationService](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationService.java) class. AuthState is designed to be easily persistable as a JSON string, using the storage mechanism of your choice (e.g. [SharedPreferences](https://developer.android.com/training/basics/data-storage/shared-preferences.html), [sqlite](https://developer.android.com/training/basics/data-storage/databases.html), or even just [in a file](https://developer.android.com/training/basics/data-storage/files.html)). AppAuth provides data classes which are intended to model the OAuth2 specification as closely as possible; this provides the greatest flexibility in interacting with a wide variety of OAuth2 and OpenID Connect implementations. Authorizing the user occurs via the user's web browser, and the request is described using instances of [AuthorizationRequest](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationRequest.java). The request is dispatched using [performAuthorizationRequest()](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationService.java#L159) on an AuthorizationService instance, and the response (an [AuthorizationResponse](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationResponse.java) instance) will be dispatched to the activity of your choice, expressed via an Intent. Token requests, such as obtaining a new access token using a refresh token, follow a similar pattern: [TokenRequest](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/TokenRequest.java) instances are dispatched using [performTokenRequest()](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationService.java#L252) on an AuthorizationService instance, and a [TokenResponse](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/TokenResponse.java) instance is returned via a callback. Responses can be provided to the [update()](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthState.java#L367) methods on AuthState in order to track and persist changes to the authorization state. Once in an authorized state, the [performActionWithFreshTokens()](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthState.java#L449) method on AuthState can be used to automatically refresh access tokens as necessary before performing actions that require valid tokens. ## Implementing the authorization code flow It is recommended that native apps use the [authorization code](https://tools.ietf.org/html/rfc6749#section-1.3.1) flow with a public client to gain authorization to access user data. This has the primary advantage for native clients that the authorization flow, which must occur in a browser, only needs to be performed once. This flow is effectively composed of four stages: 1. Discovering or specifying the endpoints to interact with the provider. 2. Authorizing the user, via a browser, in order to obtain an authorization code. 3. Exchanging the authorization code with the authorization server, to obtain a refresh token and/or ID token. 4. Using access tokens derived from the refresh token to interact with a resource server for further access to user data. At each step of the process, an AuthState instance can (optionally) be updated with the result to help with tracking the state of the flow. ### Authorization service configuration First, AppAuth must be instructed how to interact with the authorization service. This can be done either by directly creating an [AuthorizationServiceConfiguration](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationServiceConfiguration.java#L102) instance, or by retrieving an OpenID Connect discovery document. Directly specifying an AuthorizationServiceConfiguration involves providing the URIs of the authorization endpoint and token endpoint, and optionally a dynamic client registration endpoint (see "Dynamic client registration" for more info): ```java AuthorizationServiceConfiguration serviceConfig = new AuthorizationServiceConfiguration( Uri.parse("https://idp.example.com/auth"), // authorization endpoint Uri.parse("https://idp.example.com/token")); // token endpoint ``` Where available, using an OpenID Connect discovery document is preferable: ```java AuthorizationServiceConfiguration.fetchFromIssuer( Uri.parse("https://idp.example.com"), new AuthorizationServiceConfiguration.RetrieveConfigurationCallback() { public void onFetchConfigurationCompleted( @Nullable AuthorizationServiceConfiguration serviceConfiguration, @Nullable AuthorizationException ex) { if (ex != null) { Log.e(TAG, "failed to fetch configuration"); return; } // use serviceConfiguration as needed } }); ``` This will attempt to download a discovery document from the standard location under this base URI, `https://idp.example.com/.well-known/openid-configuration`. If the discovery document for your IDP is in some other non-standard location, you can instead provide the full URI as follows: ```java AuthorizationServiceConfiguration.fetchFromUrl( Uri.parse("https://idp.example.com/exampletenant/openid-config"), new AuthorizationServiceConfiguration.RetrieveConfigurationCallback() { ... } }); ``` If desired, this configuration can be used to seed an AuthState instance, to persist the configuration easily: ```java AuthState authState = new AuthState(serviceConfig); ``` ### Obtaining an authorization code An authorization code can now be acquired by constructing an AuthorizationRequest, using its Builder. In AppAuth, the builders for each data class accept the mandatory parameters via the builder constructor: ```java AuthorizationRequest.Builder authRequestBuilder = new AuthorizationRequest.Builder( serviceConfig, // the authorization service configuration MY_CLIENT_ID, // the client ID, typically pre-registered and static ResponseTypeValues.CODE, // the response_type value: we want a code MY_REDIRECT_URI); // the redirect URI to which the auth response is sent ``` Other optional parameters, such as the OAuth2 [scope string](https://tools.ietf.org/html/rfc6749#section-3.3) or OpenID Connect [login hint](http://openid.net/specs/openid-connect-core-1_0.html#rfc.section.3.1.2.1) are specified through set methods on the builder: ```java AuthorizationRequest authRequest = authRequestBuilder .setScope("openid email profile https://idp.example.com/custom-scope") .setLoginHint("jdoe@user.example.com") .build(); ``` This request can then be dispatched using one of two approaches. a `startActivityForResult` call using an Intent returned from the `AuthorizationService`, or by calling `performAuthorizationRequest` and providing pending intent for completion and cancelation handling activities. The `startActivityForResult` approach is simpler to use but may require more processing of the result: ```java private void doAuthorization() { AuthorizationService authService = new AuthorizationService(this); Intent authIntent = authService.getAuthorizationRequestIntent(authRequest); startActivityForResult(authIntent, RC_AUTH); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == RC_AUTH) { AuthorizationResponse resp = AuthorizationResponse.fromIntent(data); AuthorizationException ex = AuthorizationException.fromIntent(data); // ... process the response or exception ... } else { // ... } } ``` If instead you wish to directly transition to another activity on completion or cancelation, you can use `performAuthorizationRequest`: ```java AuthorizationService authService = new AuthorizationService(this); authService.performAuthorizationRequest( authRequest, PendingIntent.getActivity(this, 0, new Intent(this, MyAuthCompleteActivity.class), 0), PendingIntent.getActivity(this, 0, new Intent(this, MyAuthCanceledActivity.class), 0)); ``` The intents may be customized to carry any additional data or flags required for the correct handling of the authorization response. #### Capturing the authorization redirect Once the authorization flow is completed in the browser, the authorization service will redirect to a URI specified as part of the authorization request, providing the response via query parameters. In order for your app to capture this response, it must register with the Android OS as a handler for this redirect URI. We recommend using a custom scheme based redirect URI (i.e. those of form `my.scheme:/path`), as this is the most widely supported across all versions of Android. To avoid conflicts with other apps, it is recommended to configure a distinct scheme using "reverse domain name notation". This can either match your service web domain (in reverse) e.g. `com.example.service` or your package name `com.example.app` or be something completely new as long as it's distinct enough. Using the package name of your app is quite common but it's not always possible if it contains illegal characters for URI schemes (like underscores) or if you already have another handler for that scheme - so just use something else. When a custom scheme is used, AppAuth can be easily configured to capture all redirects using this custom scheme through a manifest placeholder: ```groovy android.defaultConfig.manifestPlaceholders = [ 'appAuthRedirectScheme': 'com.example.app' ] ``` Alternatively, the redirect URI can be directly configured by adding an intent-filter for AppAuth's RedirectUriReceiverActivity to your AndroidManifest.xml: ```xml <activity android:name="net.openid.appauth.RedirectUriReceiverActivity" tools:node="replace"> <intent-filter> <action android:name="android.intent.action.VIEW"/> <category android:name="android.intent.category.DEFAULT"/> <category android:name="android.intent.category.BROWSABLE"/> <data android:scheme="com.example.app"/> </intent-filter> </activity> ``` If an HTTPS redirect URI is required instead of a custom scheme, the same approach (modifying your AndroidManifest.xml) is used: ```xml <activity android:name="net.openid.appauth.RedirectUriReceiverActivity" tools:node="replace"> <intent-filter> <action android:name="android.intent.action.VIEW"/> <category android:name="android.intent.category.DEFAULT"/> <category android:name="android.intent.category.BROWSABLE"/> <data android:scheme="https" android:host="app.example.com" android:path="/oauth2redirect"/> </intent-filter> </activity> ``` HTTPS redirects can be secured by configuring the redirect URI as an [app link](https://developer.android.com/training/app-links/index.html) in Android M and above. We recommend that a fallback page be configured at the same address to forward authorization responses to your app via a custom scheme, for older Android devices. #### Handling the authorization response Upon completion of the authorization flow, the completion Intent provided to performAuthorizationRequest will be triggered. The authorization response is provided to this activity via Intent extra data, which can be extracted using the `fromIntent()` methods on AuthorizationResponse and AuthorizationException respectively: ```java public void onCreate(Bundle b) { AuthorizationResponse resp = AuthorizationResponse.fromIntent(getIntent()); AuthorizationException ex = AuthorizationException.fromIntent(getIntent()); if (resp != null) { // authorization completed } else { // authorization failed, check ex for more details } // ... } ``` The response can be provided to the AuthState instance for easy persistence and further processing: ``` authState.update(resp, ex); ``` If the full redirect URI is required in order to extract additional information that AppAuth does not provide, this is also provided to your activity: ```java public void onCreate(Bundle b) { // ... Uri redirectUri = getIntent().getData(); // ... } ``` ### Exchanging the authorization code Given a successful authorization response carrying an authorization code, a token request can be made to exchange the code for a refresh token: ```java authService.performTokenRequest( resp.createTokenExchangeRequest(), new AuthorizationService.TokenResponseCallback() { @Override public void onTokenRequestCompleted( TokenResponse resp, AuthorizationException ex) { if (resp != null) { // exchange succeeded } else { // authorization failed, check ex for more details } } }); ``` The token response can also be used to update an AuthState instance: ```java authState.update(resp, ex); ``` ### Using access tokens Finally, the retrieved access token can be used to interact with a resource server. This can be done directly, by extracting the access token from a token response. However, in most cases, it is simpler to use the `performActionWithFreshTokens` utility method provided by AuthState: ```java authState.performActionWithFreshTokens(service, new AuthStateAction() { @Override public void execute( String accessToken, String idToken, AuthorizationException ex) { if (ex != null) { // negotiation for fresh tokens failed, check ex for more details return; } // use the access token to do something ... } }); ``` This also updates the AuthState object with current access, id, and refresh tokens. If you are storing your AuthState in persistent storage, you should write the updated copy in the callback to this method. ### Ending current session Given you have a logged in session and you want to end it. In that case you need to get: - `AuthorizationServiceConfiguration` - valid Open Id Token that you should get after authentication - End of session URI that should be provided within you OpenId service config First you have to build EndSessionRequest ```java EndSessionRequest endSessionRequest = new EndSessionRequest.Builder(authorizationServiceConfiguration) .setIdTokenHint(idToken) .setPostLogoutRedirectUri(endSessionRedirectUri) .build(); ``` This request can then be dispatched using one of two approaches. a `startActivityForResult` call using an Intent returned from the `AuthorizationService`, or by calling `performEndSessionRequest` and providing pending intent for completion and cancelation handling activities. The startActivityForResult approach is simpler to use but may require more processing of the result: ```java private void endSession() { AuthorizationService authService = new AuthorizationService(this); Intent endSessionItent = authService.getEndSessionRequestIntent(endSessionRequest); startActivityForResult(endSessionItent, RC_END_SESSION); } @Override protected void onActivityResult(int requestCode, int resultCode, Intent data) { if (requestCode == RC_END_SESSION) { EndSessionResonse resp = EndSessionResonse.fromIntent(data); AuthorizationException ex = AuthorizationException.fromIntent(data); // ... process the response or exception ... } else { // ... } } ``` If instead you wish to directly transition to another activity on completion or cancelation, you can use `performEndSessionRequest`: ```java AuthorizationService authService = new AuthorizationService(this); authService.performEndSessionRequest( endSessionRequest, PendingIntent.getActivity(this, 0, new Intent(this, MyAuthCompleteActivity.class), 0), PendingIntent.getActivity(this, 0, new Intent(this, MyAuthCanceledActivity.class), 0)); ``` End session flow will also work involving browser mechanism that is described in authorization mechanism session. Handling response mechanism with transition to another activity should be as follows: ```java public void onCreate(Bundle b) { EndSessionResponse resp = EndSessionResponse.fromIntent(getIntent()); AuthorizationException ex = AuthorizationException.fromIntent(getIntent()); if (resp != null) { // authorization completed } else { // authorization failed, check ex for more details } // ... } ``` ### AuthState persistence Instances of `AuthState` keep track of the authorization and token requests and responses. This is the only object that you need to persist to retain the authorization state of the session. Typically, one would do this by storing the authorization state in SharedPreferences or some other persistent store private to the app: ```java @NonNull public AuthState readAuthState() { SharedPreferences authPrefs = getSharedPreferences("auth", MODE_PRIVATE); String stateJson = authPrefs.getString("stateJson", null); if (stateJson != null) { return AuthState.jsonDeserialize(stateJson); } else { return new AuthState(); } } public void writeAuthState(@NonNull AuthState state) { SharedPreferences authPrefs = getSharedPreferences("auth", MODE_PRIVATE); authPrefs.edit() .putString("stateJson", state.jsonSerializeString()) .apply(); } ``` The demo app has an [AuthStateManager](https://github.com/openid/AppAuth-Android/blob/master/app/java/net/openid/appauthdemo/AuthStateManager.java) type which demonstrates this in more detail. ## Advanced configuration AppAuth provides some advanced configuration options via [AppAuthConfiguration](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AppAuthConfiguration.java) instances, which can be provided to [AuthorizationService](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationService.java) during construction. ### Controlling which browser is used for authorization Some applications require explicit control over which browsers can be used for authorization - for example, to require that Chrome be used for second factor authentication to work, or require that some custom browser is used for authentication in an enterprise environment. Control over which browsers can be used can be achieved by defining a [BrowserMatcher](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/BrowserMatcher.java), and supplying this to the builder of AppAuthConfiguration. A BrowserMatcher is suppled with a [BrowserDescriptor](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/BrowserDescriptor.java) instance, and must decide whether this browser is permitted for the authorization flow. By default, [AnyBrowserMatcher](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/AnyBrowserMatcher.java) is used. For your convenience, utility classes to help define a browser matcher are provided, such as: - [Browsers](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/Browsers.java): contains a set of constants for the official package names and signatures of Chrome, Firefox and Samsung SBrowser. - [VersionedBrowserMatcher](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/VersionedBrowserMatcher.java): will match a browser if it has a matching package name and signature, and a version number within a defined [VersionRange](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/VersionRange.java). This class also provides some static instances for matching Chrome, Firefox and Samsung SBrowser. - [BrowserAllowList](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/BrowserAllowList.java): takes a list of BrowserMatcher instances, and will match a browser if any of these child BrowserMatcher instances signals a match. - [BrowserDenyList](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/browser/BrowserDenyList.java): the inverse of BrowserAllowList - takes a list of browser matcher instances, and will match a browser if it _does not_ match any of these child BrowserMatcher instances. For instance, in order to restrict the authorization flow to using Chrome or SBrowser as a custom tab: ```java AppAuthConfiguration appAuthConfig = new AppAuthConfiguration.Builder() .setBrowserMatcher(new BrowserAllowList( VersionedBrowserMatcher.CHROME_CUSTOM_TAB, VersionedBrowserMatcher.SAMSUNG_CUSTOM_TAB)) .build(); AuthorizationService authService = new AuthorizationService(context, appAuthConfig); ``` Or, to prevent the use of a buggy version of the custom tabs in Samsung SBrowser: ```java AppAuthConfiguration appAuthConfig = new AppAuthConfiguration.Builder() .setBrowserMatcher(new BrowserDenyList( new VersionedBrowserMatcher( Browsers.SBrowser.PACKAGE_NAME, Browsers.SBrowser.SIGNATURE_SET, true, // when this browser is used via a custom tab VersionRange.atMost("5.3") ))) .build(); AuthorizationService authService = new AuthorizationService(context, appAuthConfig); ``` ### Customizing the connection builder for HTTP requests It can be desirable to customize how HTTP connections are made when performing token requests, for instance to use [certificate pinning](https://www.owasp.org/index.php/Certificate_and_Public_Key_Pinning) or to add additional trusted certificate authorities for an enterprise environment. This can be achieved in AppAuth by providing a custom [ConnectionBuilder](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/connectivity/ConnectionBuilder.java) instance. For example, to custom the SSL socket factory used, one could do the following: ```java AppAuthConfiguration appAuthConfig = new AppAuthConfiguration.Builder() .setConnectionBuilder(new ConnectionBuilder() { public HttpURLConnection openConnect(Uri uri) throws IOException { URL url = new URL(uri.toString()); HttpURLConnection connection = (HttpURLConnection) url.openConnection(); if (connection instanceof HttpsUrlConnection) { HttpsURLConnection connection = (HttpsURLConnection) connection; connection.setSSLSocketFactory(MySocketFactory.getInstance()); } } }) .build(); ``` ### Issues with [ID Token](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/IdToken.java#L118) validation ID Token validation was introduced in `0.8.0` but not all authorization servers or configurations support it correctly. - For testing environments [setSkipIssuerHttpsCheck](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AppAuthConfiguration.java#L129) can be used to bypass the fact the issuer needs to be HTTPS. ```java AppAuthConfiguration appAuthConfig = new AppAuthConfiguration.Builder() .setSkipIssuerHttpsCheck(true) .build() ``` - For services that don't support nonce[s] resulting in **IdTokenException** `Nonce mismatch` just set nonce to `null` on the `AuthorizationRequest`. Please consider **raising an issue** with your Identity Provider and removing this once it is fixed. ```java AuthorizationRequest authRequest = authRequestBuilder .setNonce(null) .build(); ``` ## Dynamic client registration AppAuth supports the [OAuth2 dynamic client registration protocol](https://tools.ietf.org/html/rfc7591). In order to dynamically register a client, create a [RegistrationRequest](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/RegistrationRequest.java) and dispatch it using [performRegistrationRequest](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationService.java#L278) on your AuthorizationService instance. The registration endpoint can either be defined directly as part of your [AuthorizationServiceConfiguration](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/AuthorizationServiceConfiguration.java), or discovered from an OpenID Connect discovery document. ```java RegistrationRequest registrationRequest = new RegistrationRequest.Builder( serviceConfig, Arrays.asList(redirectUri)) .build(); ``` Requests are dispatched with the help of `AuthorizationService`. As this request is asynchronous the response is passed to a callback: ```java service.performRegistrationRequest( registrationRequest, new AuthorizationService.RegistrationResponseCallback() { @Override public void onRegistrationRequestCompleted( @Nullable RegistrationResponse resp, @Nullable AuthorizationException ex) { if (resp != null) { // registration succeeded, store the registration response AuthState state = new AuthState(resp); //proceed to authorization... } else { // registration failed, check ex for more details } } }); ``` ## Utilizing client secrets (DANGEROUS) We _strongly recommend_ you avoid using static client secrets in your native applications whenever possible. Client secrets derived via a dynamic client registration are safe to use, but static client secrets can be easily extracted from your apps and allow others to impersonate your app and steal user data. If client secrets must be used by the OAuth2 provider you are integrating with, we strongly recommend performing the code exchange step on your backend, where the client secret can be kept hidden. Having said this, in some cases using client secrets is unavoidable. In these cases, a [ClientAuthentication](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/ClientAuthentication.java) instance can be provided to AppAuth when performing a token request. This allows additional parameters (both HTTP headers and request body parameters) to be added to token requests. Two standard implementations of ClientAuthentication are provided: - [ClientSecretBasic](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/ClientSecretBasic.java): includes a client ID and client secret as an HTTP Basic Authorization header. - [ClientSecretPost](https://github.com/openid/AppAuth-Android/blob/master/library/java/net/openid/appauth/ClientSecretPost.java): includes a client ID and client secret as additional request parameters. So, in order to send a token request using HTTP basic authorization, one would write: ```java ClientAuthentication clientAuth = new ClientSecretBasic(MY_CLIENT_SECRET); TokenRequest req = ...; authService.performTokenRequest(req, clientAuth, callback); ``` This can also be done when using `performActionWithFreshTokens` on AuthState: ```java ClientAuthentication clientAuth = new ClientSecretPost(MY_CLIENT_SECRET); authState.performActionWithFreshTokens( authService, clientAuth, action); ``` ## Modifying or contributing to AppAuth This project requires the Android SDK for API level 25 (Nougat) to build, though the produced binaries only require API level 16 (Jellybean) to be used. We recommend that you fork and/or clone this repository to make modifications; downloading the source has been known to cause some developers problems. For contributors, see the additional instructions in [CONTRIBUTING.md](https://github.com/openid/AppAuth-Android/blob/master/CONTRIBUTING.md). ### Building from the Command line AppAuth for Android uses Gradle as its build system. In order to build the library and app binaries, run `./gradlew assemble`. The library AAR files are output to `library/build/outputs/aar`, while the demo app is output to `app/build/outputs/apk`. In order to run the tests and code analysis, run `./gradlew check`. ### Building from Android Studio In AndroidStudio, File -> New -> Import project. Select the root folder (the one with the `build.gradle` file).