What is AngularJS and Why it is considered as an emerging JavaScript Framework?

AngularJS is a very powerful and most emerging JavaScript Framework.It is used in Single Page Application (SPA) projects. It extends HTML DOM with additional attributes and makes it more responsive to user actions. AngularJS is open source, completely free, and used by thousands of developers around the world.

If you want to learn AngularJS, you must have an understanding of HTML, CSS, JavaScript and AJAX, etc.

Brief History of AngularJS

AngularJS is an open source web application framework. It was originally developed in 2009 by Misko Hevery and Adam Abrons. It is now officially supported by Google. According to official documentation of AngularJS its definition is:

"AngularJS is a structural framework for dynamic web apps. It lets you use HTML as your template language and lets you extend HTML's syntax to express your application's components clearly and succinctly. Angular's data binding and dependency injection eliminate much of the code you currently have to write. And it all happens within the browser, making it an ideal partner with any server technology."


AngularJS Features


  • AngularJS is a powerful JavaScript based development framework to create RICH Internet Application(RIA).
  • AngularJS provides developers options to write client side application (using JavaScript) in a clean MVC(Model View Controller) way.
  • Application written in AngularJS is cross-browser compliant. AngularJS automatically handles JavaScript code suitable for each browser.
  • AngularJS is open source, completely free, and used by thousands of developers around the world. It is licensed under the Apache License version 2.0.

Overall, AngularJS is a framework to build large scale and high performance web application while keeping them as easy-to-maintain.




Advantages of AngularJS



  • AngularJS provides capability to create Single Page Application in a very clean and maintainable way.
  • AngularJS provides data binding capability to HTML thus giving user a rich and responsive experience
  • AngularJS code is unit testable.
  • AngularJS uses dependency injection and make use of separation of concerns.
  • AngularJS provides reusable components.
  • With AngularJS, developer write less code and get more functionality.
  • In AngularJS, views are pure html pages, and controllers written in JavaScript do the business processing.
On top of everything, AngularJS applications can run on all major browsers and smart phones including Android and iOS based phones/tablets.


Advantages of Components

The AngularJS framework can be divided into following three major parts −

  • ng-app − This directive defines and links an AngularJS application to HTML.
  • ng-model − This directive binds the values of AngularJS application data to HTML input controls.
  • ng-bind − This directive binds the AngularJS Application data to HTML tags.


AngularJS Setup

You really do not need to set up your own environment to start learning AngularJS. Reason is there is lot of AngularJS environment online, so that you can execute all the available examples online at the same time when you are doing your theory work. This gives you confidence in what you are reading and to check the result with different options. You can modify the samples and execute it to see your expected results. However if you want to setup the environment at your local machine then you to download AngularJS library from below official site:

https://angularjs.org

The latest current stable version of angularJS is  v1.6.6.

AngularJS Example

Now let us write a simple example using AngularJS library. Let us create a simple HTML file AngularWorld.html as below:
<!doctype html>
<html>
   
   <head>
      <script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.6.6/angular.min.js"></script>
   </head>
   
   <body ng-app = "myapp">
      
      <div ng-controller = "HelloController" >
         <h2>Welcome {{helloTo.title}} to learn AngularJS!</h2>
      </div>
      
      <script>
         angular.module("myapp", [])
         
         .controller("HelloController", function($scope) {
            $scope.helloTo = {};
            $scope.helloTo.title = "naeemgik";
         });
      </script>
      
   </body>
</html>





Now lets explain the above code line by line;



In order to include the angularJS file in your page, we have included it using CDN access like:

<head>
   <script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.6.6/angular.min.js"></script>
</head>


Next we tell what part of the HTML contains the AngularJS app. This done by adding the ng-app attribute to the root HTML element of the AngularJS app. You can either add it to html element or body element as shown below:

<body ng-app = "myapp">
</body>

The view part of the above example is:

<div ng-controller = "HelloController" >
   <h2>Welcome {{helloTo.title}} to learn AngularJS!</h2>
</div>

ng-controller tells AngularJS what controller to use with this view. helloTo.title tells AngularJS to write the "model" value named helloTo.title to the HTML at this location.
The controller part of the above example is:

<script>
   angular.module("myapp", [])
   
   .controller("HelloController", function($scope) {
      $scope.helloTo = {};
      $scope.helloTo.title = "naeemgik";
   });
</script>



This code registers a controller function named HelloController in the angular module named myapp. The controller function is registered in angular via the angular.module(...).controller(...) function call.



The $scope parameter passed to the controller function is the model. The controller function adds a helloTo JavaScript object, and in that object it adds a title field.



When you execute the above sample program its out will be look like:


Welcome naeemgik to learn AngularJS!


When the page is loaded in the browser, following things happens:

HTML document is loaded into the browser, and evaluated by the browser. AngularJS JavaScript file is loaded, the angular global object is created. Next, JavaScript which registers controller functions is executed.

Next AngularJS scans through the HTML to look for AngularJS apps and views. Once view is located, it connects that view to the corresponding controller function.


Next, AngularJS executes the controller functions. It then renders the views with data from the model populated by the controller. The page is now ready.


Execute shell command from Java

Sometime we need to execute shell commands from java code. Like in case where we use jar file in our java code and running that jar from shell command like java -jar <jar_name.jar> or in order to find java version from shell command like java -verison

In this tutorial I am going to write a sample program wich execute the same command from java code.


CmdTest.java

import java.io.*;

public class CmdTest
{
 

public static void main(String[] args) throws Exception
{
String arg1 = "cmd.exe";
String commandToExec = "java -version";

final String folder= System.getProperty("user.dir")+"/lib\"";
String[] command = { arg1, "/C", "cd \""+folder+"&&"+commandToExec};

ProcessBuilder builder = new ProcessBuilder(command);
builder.redirectErrorStream(true);
Process p = builder.start();
BufferedReader r = new BufferedReader(new InputStreamReader(p.getInputStream()));
String line;
while (true)
{
line = r.readLine();
if (line == null)
{
break;
}

System.out.println(line);
}
}
}

Output:


java version "1.8.0_77"
Java(TM) SE Runtime Environment (build 1.8.0_77-b03)
Java HotSpot(TM) 64-Bit Server VM (build 25.77-b03, mixed mode)



8 features of java 8

JAVA 8 or JDK 1.8 is a major release of JAVA language. Its initial version was released on 18 March 2014. With the Java 8 release, Java provided support for functional programming, new JavaScript engine, new APIs for date time manipulation, new streaming API and many more.


8 New Features of Java 8



The most significant features of java 8 are below:

Lambda expression: 

It adds functional processing capability to Java. A new language feature, has been introduced in this release. They enable you to treat functionality as a method argument, or code as data. Lambda expressions let you express instances of single-method interfaces (referred to as functional interfaces) more compactly.

Method references: 

Referencing functions by their names instead of invoking them directly. Using functions as parameter. Provide easy-to-read lambda expressions

Default method: 

Default methods enable new functionality to be added to the interfaces of libraries and ensure binary compatibility with code written for older versions of those interfaces.


Stream API: 

New Stream API (java.util.stream ) to support functional-style operations on streams of elements. The Stream API is integrated into the Collections API, which enables bulk operations on collections, such as sequential or parallel map-reduce transformations.

Date Time API: 

The Date/Time API is moved to java.time package and Joda time format is followed. Another good news is that, most classes are Thread safe and immutable.

Nashorn, JavaScript Engine: 

A Java-based engine to execute JavaScript code. It is similar to the V8 engine provided by chrome over which Node.js runs. It is compatible with Node.js applications while also allowing actual Java libraries to be called by the javascript code running on server. This is exciting to say at the least as it marries scalability and asynchronous nature of Node.js with safe and widespread server side Java middleware directly.


New tools:

New compiler tools and utilities are added like ‘jdeps’ to figure out dependencies.

Optional Values:

Emphasis on best practices to handle null values properly. Java SE 8 introduces a new class called java.util.Optional that can alleviate some of these problems.

References: 
http://www.oracle.com/technetwork/java/javase/8-whats-new-2157071.html

Java 8 - Lambda Expressions

Lambda expressions are introduced in Java 8 and are assumed to be the biggest feature of Java 8. Lambda expression facilitates functional programming, and it simplifies the development very much.
A lambda expression represents an anonymous function. It comprises of a set of parameters, a lambda operator (->) and a function body.

Syntax

A lambda expression is characterized by the following syntax:

parameter -> expression body

Following are the important characteristics of a lambda expression

Optional type declaration: No need to declare the type of a parameter. The compiler can inference the same from the value of the parameter.

Optional parenthesis around parameter:  No need to declare a single parameter in parenthesis. For multiple parameters, parentheses are required.
Optional curly braces: No need to use curly braces in expression body if the body contains a single statement.
Optional return keyword: The compiler automatically returns the value if the body has a single expression to return the value. Curly braces are required to indicate that expression returns a value.



Lambda Expressions Example


Create the following Java program using eclipse editor

LambdaExpressionTest.java

public class LambdaExpressionTest {
public static void main(String args[]) {
LambdaExpressionTest test = new LambdaExpressionTest();

// with type declaration
MathOperation addition = (int a, int b) -> a + b;

// with out type declaration
MathOperation subtraction = (a, b) -> a - b;

// with return statement along with curly braces
MathOperation multiplication = (int a, int b) -> {
return a * b;
};

// without return statement and without curly braces
MathOperation division = (int a, int b) -> a / b;

System.out.println("10 + 5 = " + test.operate(10, 5, addition));
System.out.println("10 - 5 = " + test.operate(10, 5, subtraction));
System.out.println("10 x 5 = " + test.operate(10, 5, multiplication));
System.out.println("10 / 5 = " + test.operate(10, 5, division));

// without parenthesis
GreetingService greetService1 = message -> System.out.println("Hi " + message);

// with parenthesis
GreetingService greetService2 = (message) -> System.out.println("Hi " + message);

greetService1.sayMessage("Guest");
greetService2.sayMessage("User");
}

interface MathOperation {
int operation(int a, int b);
}

interface GreetingService {
void sayMessage(String message);
}

private int operate(int a, int b, MathOperation mathOperation) {
return mathOperation.operation(a, b);
}
}

When you execute the program its output look like:

10 + 5 = 15
10 - 5 = 5
10 x 5 = 50
10 / 5 = 2
Hi Guest
Hi Welcome to my blog

Important points to be considered from above example.


Lambda expressions are used primarily to define inline implementation of a functional interface, i.e., an interface with a single method only. In the above example, we've used various types of lambda expressions to define the operation method of MathOperation interface. Then we have defined the implementation of sayMessage of GreetingService.

Lambda expression eliminates the need of anonymous class and gives a very simple yet powerful functional programming capability to Java.