Simple threads in Java

Sep 11, 2012 java

In Java, a thread is a separate path of execution within a program. A java application always starts with the main-thread. There are two most common ways to create simple threads in java

By extending java.lang.Thread class or
By implementing java.lang.Runnable interface

In both cases, we have to provide the code block which will be executed in run method. These statements are executed on a separate path other than main-thread. Thread class itself internally implements Runnable interface.

By extending Thread class

 1class ThreadSubClass extends Thread {
 2   public ThreadSubClass(String name) {
 3       super(name);
 4   }
 5
 6   @Override
 7   public void run() {
 8       String output = String.format("Thread code running on %s", Thread.currentThread().getName());
 9       System.out.println(output);
10   }
11}

By implementing Runnable interface

1class RunnableClass implements Runnable {
2 
3   @Override
4   public void run() {
5       String output = String.format("Runnable code running on %s", Thread.currentThread().getName());
6       System.out.println(output);
7   }
8}

Program

 1public class SimpleThreadInJava {
 2
 3   public static void main(String[] args) {
 4       System.out.printf("Current Application Thread - %s%n", Thread.currentThread().getName());
 5       Thread thread1 = new ThreadSubClass("CustomThreadExtended-0");
 6       Thread thread2 = new Thread(new RunnableClass(), "Runnable-0");
 7       thread1.start();
 8       thread2.start();
 9   }
10}

Output

1Current Application Thread - main
2Thread code running on CustomThreadExtended-0
3Runnable code running on Runnable-0

Creating thread is costly, always be careful when creating new Thread() inside loops.

Ref

https://docs.oracle.com/javase/tutorial/essential/concurrency/index.html