Java Threading - Three ways to create java threads

In programming, threading is a way of distributing our work. We can delegate a huge load of work in to several threads (i.e several processes). A thread will run as a separate operating system process which can run concurrently with other threads.

There are three ways of creating threads in java

1. Extend the thread class

Thread class has a run method and need override method with the code to run in a its own thread.

	class Runner extends Thread{
	@Override
	public void run() {
	for(int i=0;i<10;i++){
	System.out.println("Hello "+i);
	try{
	Thread.sleep(100);
	}catch(InterruptedException e){
	e.printStackTrace();
	}
	}
	}
	}
	public class App {
	public static void main(String args[]){
	Runner runner1= new Runner();
	runner1.start();
	Runner runner2 = new Runner();
	runner2.start();
	}
	}

view raw JavaThread1_1.java hosted with ❤ by GitHub

To execute code in a separate thread,

• Instantiate an object of class which is extended by Thread class (Runner)
• Invoke the start() method of Thread class.
• start() method will go to Thread class and look for the run method and invoke that in a separate thread.

2. Implement Runnable interface

• Implement Runnable interface in a class
• Pass object of that class to a constructor of Thread class.
• Invoke the start() method 

	class Runner implements Runnable{
	@Override
	public void run() {
	for(int i=0;i<10;i++){
	System.out.println("Hello "+i);
	try{
	Thread.sleep(100);
	}catch(InterruptedException e){
	e.printStackTrace();
	}
	}
	}
	}
	public class App {
	public static void main(String args[]){
	Thread t1 = new Thread(new Runner());
	Thread t2 = new Thread(new Runner());
	t1.start();
	t2.start();
	}
	}

view raw JavaThread1_2.java hosted with ❤ by GitHub

3. Instantiate a Thread object with a Runnable instance

	public class App2 {
	public static void main(String args[]){
	Thread t1 = new Thread(new Runnable(){
	@Override
	public void run() {
	for(int i=0;i<10;i++){
	System.out.println("Hello "+i);
	try{
	Thread.sleep(100);
	}catch(InterruptedException e){
	e.printStackTrace();
	}
	}
	}
	});
	t1.start();
	}
	}

view raw JavaThread1_3.java hosted with ❤ by GitHub

Java Socket Programming - Simple Server And Client

In Java socket programming(Network programming) we basically study about how to implement programs that communicate over a network. When we use java to implement those kind of applications java.net package will be used because it contains collection of classes and interfaces that provide low level communication details. It provides support for TCP and UDP which are two major network protocols.

Process between client and a server

• First client program creates a socket and try to connect to a socket in a server. That server socket should be already created and ready for client requests. 
• After a connection is made server and client communicate by writing and reading from the socket.