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      Course
      Starting a Thread

      Java Tutorial

      This Java tutorial is tailored for newcomers, offering a journey from basic principles to complex Java programming techniques. Completing this tutorial equips you with a solid understanding of Java, preparing you for advanced learning. You'll emerge ready to tackle the challenges of becoming a top-tier software engineer, with the skills to innovate and excel in the vast world of software development.

      Starting a Thread

      Starting a Thread

      Once a Thread object is created, you can start it by calling start() method, which executes a call to run() method. Following is a simple syntax of start() method 
      void start();

      Syntax of Starting a Thread

      The following is the syntax of starting a thread 
      thread_obj.start();
      Here, thread_obj is an object to the Thread class, and start() is the method of the Thread class.

      Start a Thread by Implementing Runnable Interface

      In this example, we're creating a class RunnableDemo by implementing Runnable interface. RunnableDemo class has run() method implementation. In main class TestThread, we've created the RunnableDemo objects and using those objects we've created two Thread objects. When Thread.start() method is called on each thread objects, threads start processing and program is executed.

      Example

      package com.tutorialspoint;
      class RunnableDemo implements Runnable {
         private String threadName;
         RunnableDemo( String name) {
            threadName = name;
            System.out.println("Thread: " + threadName + ", " + "State: New");
         }
         public void run() {
            System.out.println("Thread: " + threadName + ", " + "State: Running");
            for(int i = 4; i > 0; i--) {
               System.out.println("Thread: " + threadName + ", " + i);         
            }
            System.out.println("Thread: " + threadName + ", " + "State: Dead");
         }
      }
      public class TestThread {
         public static void main(String args[]) {
      	  RunnableDemo runnableDemo1 = new RunnableDemo( "Thread-1");
      	  RunnableDemo runnableDemo2 = new RunnableDemo( "Thread-2");	  
      	  Thread thread1 = new Thread(runnableDemo1);
      	  Thread thread2 = new Thread(runnableDemo2);
      	  thread1.start();
      	  thread2.start();
         }
      }

      Output

      Thread: Thread-1, State: New
      Thread: Thread-2, State: New
      Thread: Thread-1, State: Running
      Thread: Thread-1, 4
      Thread: Thread-1, 3
      Thread: Thread-1, 2
      Thread: Thread-1, 1
      Thread: Thread-1, State: Dead
      Thread: Thread-2, State: Running
      Thread: Thread-2, 4
      Thread: Thread-2, 3
      Thread: Thread-2, 2
      Thread: Thread-2, 1
      Thread: Thread-2, State: Dead

      Start a Thread by Extending Thread Class

      Here is the preceding program rewritten to extend the Thread − In this example, we've created a ThreadDemo class which extends Thread class. We're calling super(name) in constructor() method to assign a name to the thread and called super.start() to start the thread processing.

      Example

      package com.tutorialspoint;
      class ThreadDemo extends Thread {
         ThreadDemo( String name) {
      	  super(name);
            System.out.println("Thread: " + name + ", " + "State: New");
         }
         public void run() {
            System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
            for(int i = 4; i > 0; i--) {
               System.out.println("Thread: " + Thread.currentThread().getName() + ", " + i); 
            }
            System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
         }
         public void start () {
            System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
            super.start();
         }
      }
      public class TestThread {
         public static void main(String args[]) {
      	  ThreadDemo thread1 = new ThreadDemo( "Thread-1");
      	  ThreadDemo thread2 = new ThreadDemo( "Thread-2");
      	  thread1.start();
      	  thread2.start();
         }
      }

      Output

      Thread: Thread-1, State: New
      Thread: Thread-2, State: New
      Thread: Thread-1, State: Running
      Thread: Thread-1, 4
      Thread: Thread-1, 3
      Thread: Thread-1, 2
      Thread: Thread-1, 1
      Thread: Thread-1, State: Dead
      Thread: Thread-2, State: Running
      Thread: Thread-2, 4
      Thread: Thread-2, 3
      Thread: Thread-2, 2
      Thread: Thread-2, 1
      Thread: Thread-2, State: Dead

      Start a Thread (with Demonstrating sleep() method)

      In this example, we're creating couple of objects of ThreadDemo class which extends Thread class. We're calling super(name) in constructor() method to assign a name to the thread and called super.start() to start the thread processing. Using sleep() method, we're introducing the delay in processing.

      Example

      package com.tutorialspoint;
      class ThreadDemo extends Thread {
         ThreadDemo( String name) {
      	  super(name);
            System.out.println("Thread: " + name + ", " + "State: New");
         }
         public void run() {
            System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Running");
            for(int i = 4; i > 0; i--) {
               System.out.println("Thread: " + Thread.currentThread().getName() + ", " + i); 
               try {
      			Thread.sleep(50);
      		} catch (InterruptedException e) {
      			// TODO Auto-generated catch block
      			e.printStackTrace();
      		}
            }
            System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Dead");
         }
         public void start () {
            System.out.println("Thread: " + Thread.currentThread().getName() + ", " + "State: Start");
            super.start();
         }
      }
      public class TestThread {
         public static void main(String args[]) {
      	   ThreadDemo thread1 = new ThreadDemo( "Thread-1");
      	   ThreadDemo thread2 = new ThreadDemo( "Thread-2");
      	  thread1.start();
      	  thread2.start();
         }
      }

      Output

      Thread: Thread-1, State: New
      Thread: Thread-2, State: New
      Thread: main, State: Start
      Thread: main, State: Start
      Thread: Thread-1, State: Running
      Thread: Thread-1, 4
      Thread: Thread-2, State: Running
      Thread: Thread-2, 4
      Thread: Thread-2, 3
      Thread: Thread-1, 3
      Thread: Thread-1, 2
      Thread: Thread-2, 2
      Thread: Thread-2, 1
      Thread: Thread-1, 1
      Thread: Thread-1, State: Dead
      Thread: Thread-2, State: Dead