A thread is the smallest unit of execution within a program, allowing multiple tasks to run concurrently. In Java, threads help improve performance by enabling parallel execution.

• Created using the Thread class or Runnable interface
• Starts execution with start() which internally calls run()
• Enables concurrent execution of multiple tasks

Note: Every class that is used as a thread must implement Runnable interface and override its run method.

Syntax

public class Thread extends Object implements Runnable

Constructors of Thread Class

Example: Java program to demonstrate usage of Thread class 

class MyThread extends Thread 
{
  	// Overriding the run method
  	@Override
    public void run() 
    {
        for (int i = 0; i < 5; i++) 
        {
            System.out.println(Thread.currentThread().getName()
                               + " - Count : " + i);
            
          	try {
              	// Sleep for 500 milliseconds
                Thread.sleep(500); 
            } 
          	catch (InterruptedException e) {
                System.out.println("Thread interrupted");
            }
        }
    }
}

// Main Class
public class Geeks 
{
    public static void main(String[] args) 
    {
        MyThread thread1 = new MyThread();
        MyThread thread2 = new MyThread();

        thread1.setName("Thread 1");
        thread2.setName("Thread 2");

      	// Start thread 1
        thread1.start(); 
      
      	// Start thread 2
        thread2.start(); 
    }
}

Output:

Thread 1 - Count : 0
Thread 2 - Count : 0
Thread 1 - Count : 1
Thread 2 - Count : 1
Thread 1 - Count : 2
Thread 2 - Count : 2
Thread 1 - Count : 3
Thread 2 - Count : 3
Thread 2 - Count : 4
Thread 1 - Count : 4

Note: Execution of the thread is not according to the sequence, it can be executed in any sequence Thread 1 then Thread 2 , or Thread 2 then Thread 1.

Methods of Thread Class

Methods Inherited from java. lang.Object Class 

• equals()
• finalize()
• getClass()
• hashCode()
• notify()
• notifyAll()
• toString()
• wait()