Threading in Java

Introduction

Until now, the programs we have discussed so far were sequential ones, i.e. each of the them has a beginning, an execution sequence, and an end. While the program is being executed, at any point of time, there is a single line of execution. One thing that you must note that a thread in itself is not a program, as it cannot run on its own. However it can be embedded with any other program.

A thread is a single sequential flow of control within a program.

There are many definition of thread some of the A thread is a lightweight process, a thread is a basic processing unit to which an operating system allocates processor time and more than one thread can be executing code inside a process.

States of thread

1-New-This is a state when a thread is not started. But the thread is created.

2-Runnable- This is the execution state of the thread.

3-Blocked- This is the state when a thread is waiting for a lock to access an object.

4-Waiting-In this state a thread is waiting indefinitely for another thread to perform an action.

5-Timed__Waiting. A state in which a thread is waiting for up to a specified period of time for another thread to perform an action.

6-Not Runnable- after Runnable states these three states are assumed to be in a not Runnable state. These three states are waiting, Timed_waiting and Terminated.

7-Terminated- In this state the thread is dead.

Life Cycle of a thread

Crating a thread

There are two ways for creating a thread.

Method-1 : By extend the Thread class of java.lang package.

Syntax

class MyThread extends Thread

{

-----------------;

}

The run( ) method has to be Overridden by writing codes required for the thread. The thread behaves as per this code segment.

public void run()

{

----------------;

}

Example- In this Example we are going to create a thread with the help of the extends Thread class.

class MyThread extends Thread
{
int i;
MyThread(int i)
{
this.i=i;
}
public void run() //this method overrid from thread class
{
while(true)
{
System.out.println("abhishek kumar dubey:"+i++);
try
{
Thread.sleep(1500); // use for break 1500 mili second
}
catch(InterruptedException e)
{
System.out.println(e);
}
if (i==15 ) // use for terminate the infinite loop
{
System.out.println(Thread.currentThread());
break;
}
}
}
}
public class TestThread
{
public static void main(String []args)
{
MyThread m1=new MyThread(1);
m1.start(); // for start thread
System.out.println(Thread.currentThread());
}
}

Output:

Method :2 By Implements Runnable Interface.

Note- If you make a thread by using Runnable Interface then it must override the run() method.

public MyThread implements Runnable {
-----------
-----------

public void run() {
------

------
}
}

Example-

import java.lang.*;
class Runner1 implements Runnable {
int i;
public void run() //this method overrid from Runnable interface must be,fuctionality as per reqairements
{
i = 0;
while (true) {
System.out.println("Runner_first" + i++);
if (i == 10)
break;
}
}
}
class Runner2 implements Runnable {
int i;
public void run() {
i = 0;
while (true) {
System.out.println("Runner_second" + i++);
if (i == 10)
break;
}
}
}
public class ThreadDemo {
public static void main(String[] args) {
Runner1 r = new Runner1();
Thread t = new Thread(r); // I M P
/*from here run() method call which is override in Runner class*/
t.start(); // for start thread 4 execution
Runner2 r1 = new Runner2();
Thread t1 = new Thread(r1);
/*from here run() method call which is override in Runner class*/
t1.start();
}
}

Output

Summary

In this article, we learned about Threading in Java and creation of threads in our Java program.

Resource

A Complete MultiThreading Tutorial in Java

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