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Unit 5

Multithreading in Java

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Concurrency and Synchronization, Java Thread Model: Thread priorities, Synchronization, Messaging, Main Thread, Creating thread: Implementing Thread using thread class and Runnable interface. Creating multiple threads using isAlive() and join()

Web Based Application in Java: Use of JavaScript for creating web based applications in java, Introduction to javascript frameworks- React, Vue, Angular

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Application of Multithreading

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  • A program with multiple threads running within a single instance could be considered as a multitasking system within an OS.

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class Create extends Thread

{

Create()

{

super("ABC");

start();

}// Constructor Closed

public void run()

{

try {

for(int i = 0;i<5;i++)

{ System.out.println("Child : " +i);

Create Thread by Extending Thread Class

Thread.sleep(500);

} //for close

}catch(InterruptedException e){ }

System.out.println("Child Exiting");

} //run() close

public static void main(String[] args)

{

Create c = new Create();

try {

for(int i = 0;i<5;i++)

{ System.out.println("Mainthread"+i);

Thread.sleep(1000);

} //for close

}catch(InterruptedException e) { }

System.out.println("Main Exiting");

} }

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Child : 0

Mainthread0

Child : 1

Mainthread1

Child : 2

Child : 3

Mainthread2

Child : 4

Child Exiting

Mainthread3

Mainthread4

Main Exiting

...Program finished with exit code 0

Press ENTER to exit console.

Create Thread by Extending Thread Class..Output

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class Create implements Runnable {

Thread t;

Create()

{

t = new Thread(this,”DemoThread”);

t.start();

}// Constructor Closed

public void run()

{

try {

for(int i = 0;i<5;i++)

{ System.out.println("Child : " +i);

Create Thread by Implementing Runnable

Thread.sleep(500);

} //for close

}catch(InterruptedException e){ }

System.out.println("Child Exiting");

} //run() close

public static void main(String[] args)

{

Create c = new Create();

try {

for(int i = 0;i<5;i++)

{ System.out.println("Mainthread"+i);

Thread.sleep(1000);

} //for close

}catch(InterruptedException e) { }

System.out.println("Main Exiting");

} }

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Main Thread

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The general form of currentThread method is :

static Thread currentThread();

Hence it can be invoked as follows :

Thread.currentThread();

For Ex :

Main Thread

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class Demo

{

public static void main(String args[])

{

Thread t = Thread.currentThread( );

System.out.println(“The Thread is : “ +t);

}

}

O/p : The Thread is : Thread[main,5,main]

In the output Thread[main,5,main] : The order is :

[Name of thread , Priority of thread , & Group of thread]

Main Thread

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Main Thread

class Demo

{

public static void main(String args[])

{

Thread t = Thread.currentThread( );

System.out.println(“The Thread is : “ +t);

t.setName(“First Thread”);

System.out.println(“The new name is : “ +t);

int p = t.getPriority( );

System.out.println(“The Thread priority is : “ +p);

t.setPriority(10);

System.out.println(“The new priority is : “ +t.getPriority( ));

}

}

OUTPUT

The Thread is : Thread[main,5,main]

The new name is : [First Thread,5,main]

The Thread priority is : 5

The new priority is : 10

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Synchronization

class Table{

synchronized void printTable(int n){

//method not synchronized

for(int i=1;i<=5;i++){

System.out.println(n*i);

try{

Thread.sleep(400);

}catch(Exception e){System.out.println(e);}

} //for close

} }

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Synchronization..>Contd

class MyThread1 extends Thread{

Table t;

MyThread1(Table t){

this.t=t;

}

public void run(){

t.printTable(5);

}

}

class MyThread2 extends Thread{

Table t;

MyThread2(Table t){

this.t=t;

}

public void run(){

t.printTable(100);

}

}

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class TestSynchronization1{

public static void main(String args[]){

Table obj = new Table();//only one object

MyThread1 t1=new MyThread1(obj);

MyThread2 t2=new MyThread2(obj);

t1.start();

t2.start();

}

}

​

OUTPUT

5

10

15

20

25

100

200

300

400

500

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Synchronization…Contd

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wait()

join()

It is a method of java.lang.Object class.

It is a method of java.lang.Thread

wait() method can be called by a synchronized block or method.

It is used to stop the current thread.

wait() method is implemented for performing multi-thread-synchronization.

It can be called either with synchronized and without synchronized context.

Its syntax is -:

public final void wait() throws InterruptedException

Its syntax is -:

public final void join() throws InterruptedException

wait() method causes the thread to sleep until notify() and notifyAll() are called

It can be used to add sequence among more than one thread

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Web Based Application in Java: Use of JavaScript for creating web based applications in java, Introduction to javascript frameworks- React, Vue, Angular

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Web Application Development

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Static VS Dynamic

  • HTML documents are usually static
  • The contents can only be changed manually
  • There are needs for dynamic documents
    • Search results
    • Database access
    • Context sensitive reply
  • Static
    • page appears exactly as it was encoded, nothing changes
  • Dynamic
    • page is compiled, or able to be changed

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Scripts: Server-Side VS Client-Side

  • Server-side
    • the first type possible on the Web
    • action occurs at the server
  • Client-side
    • generally easier to implement
    • may be prepared and implemented offline
    • action occurs on the client side (browser)

​

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JAVASCRIPT

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LIBRARY Vs FRAMEWORK

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JAVA SCRIPT

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JAVASCRIPT FEATURES

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NEED/ADVANTAGES OF JAVASCRIPT

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Use to structure and give meaning to our web content, for example defining paragraphs, headings, and data tables, or embedding images and videos in the page.

To apply styling to our HTML content, for example setting background colors and fonts, and laying out our content in multiple columns.

To create dynamically updating content, control multimedia, animate images.

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<p>Player 1: Chris</p>

​

​

​

p {

font-family: 'helvetica neue', helvetica, sans-serif;

letter-spacing: 1px;

text-transform: uppercase;

text-align: center;

border: 2px solid rgba(0,0,200,0.6);

background: rgba(0,0,200,0.3);

color: rgba(0,0,200,0.6);

box-shadow: 1px 1px 2px rgba(0,0,200,0.4);

border-radius: 10px;

padding: 3px 10px;

display: inline-block;

cursor: pointer;

}

​

const para = document.querySelector('p');

​

para.addEventListener('click', updateName);

​

function updateName() {

const name = prompt('Enter a new name');

para.textContent = `Player 1: ${name}`;

}

​

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JavaScript - Coding Ways/ Script Placement

Script in

<head>...</head> section.

Script in

<body>...</body> section.

Script in

<head>and <body> section.

Script in an external file and then include in <head>...</head> section.

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JavaScript - Coding Ways/ Script Placement

Script in

<head>...</head> section.

Script in

<body>...</body> section.

In HTML, JavaScript code is inserted between

<script> and </script> tags.

Script in

<head>and <body> section.

Script in an external file and then include in <head>...</head> section.

Note

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JavaScript - Example 1

Script in

<head>...</head> section.

<html>

<head>

<script>

document.write("Hello World")

</script>

</head>

</html>

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Example 2

Script in an external file and then include in <head>...</head> section.

<html>

<head>

<script type = "text/javascript" src = "filename.js" ></script>

</head>

<body>

<h2>Demo External JavaScript</h2>

​

<button type="button" onclick="sayHello()">Try it</button>

</body>

</html>

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Example 2 : Output

Script in an external file and then include in <head>...</head> section.

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JavaScript - Vue

Open Source

Used to develop interactive web interfaces.

VueJS focusses on the view layer

It is easily integrated into big projects for front-end development without any issues.

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<html>

<head>

<title>VueJs Introduction</title>

<script type = "text/javascript" src = "js/vue.js"></script>

</head>

<body>

<div id = "intro" style = "text-align:center;">

<h1>{{ message }}</h1>

</div>

<script type = "text/javascript">

var vue_det = new Vue({

el: '#intro',

data: {

message: 'My first VueJS Task'

}

}); </script> </body> </html>

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Example Vue : Output

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JavaScript - AngularJs

Powerful JavaScript Framework.

Used in Single Page Application (SPA) projects

Open Source

It extends HTML DOM with additional attributes and makes it more responsive to user actions

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JavaScript - AngularJs

It Uses Model View Controller Architecture

AngularJS framework can be divided into three major parts

  • Model - maintains the data
  • View : Display of data/Appearance of data
  • Controller : Interface between model and View

ng-app

ng-model

ng-bind

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JavaScript - AngularJs

ng-app

ng-model

ng-bind

This directive defines and links an AngularJS application to HTML.

This directive binds the values of AngularJS application data to HTML input controls.

This directive binds the AngularJS application data to HTML tags.

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<html>

<head>

<title>AngularJS First Application</title>

</head>

<body>

<h1>Sample Application</h1>

<div ng-app = "">

<p>Enter your Name: <input type = "text" ng-model = "name"></p>

<p>Hello <span ng-bind = "name"></span>!</p>

</div>

<script src = "https://ajax.googleapis.com/ajax/libs/angularjs/1.3.14/angular.min.js">

</script>

</body>

</html>

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  • Angular, developed by Google, was first released in 2010, making it the oldest of the lot. It is a TypeScript-based JavaScript framework.
  • React, developed by Facebook, was initially released in 2013. Facebook uses React extensively in their products (Facebook, Instagram, and WhatsApp).
  • Vue, also known as Vue.js, is the youngest member of the group. It was developed by ex-Google employee Evan You in 2014.

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End of Unit 5

Thank You!!!

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