Print Even and Odd Numbers Using Two Threads in Java

Learn how to print even and odd numbers using two threads in Java with a simple multithreading example. In this example, we create separate threads for odd and even numbers.

Code Explanation (Step-by-Step)

  • Create a TaskOddEven class that extends the Thread class. The class has a parameterized constructor that accepts the thread name and starting number.
  • Create the first thread object t1 by passing “Odd Thread : ” as the name and 1 as the starting number.
  • Create the second thread object t2 by passing “Even Thread : ” as the name and 2 as the starting number.
  • Now Call start() to start the odd-number thread. The start() method causes the run() method to execute on a new thread.
  • Inside the run() method, iterate the for loop four times. The number starts from 1 and is incremented by 2 after each iteration: 1, 3, 5, 7
  • After Call start() to start the even-number thread. Its run() method also iterates four times.
  • The even number starts from 2 and is incremented by 2 after each iteration: 2, 4, 6, 8
  • Since both threads execute independently, the exact order of odd and even output is not guaranteed.
				
					class TaskOddEven extends Thread {

    private int number;
    private String name;

    public TaskOddEven(String name, int number) {
        this.name = name;
        this.number = number;
    }

    @Override
    public void run() {
        for (int i = 0; i < 4; i++) {
            System.out.println(name + number);
            number += 2;
        }
    }
}

public class PrintOddEven {

    public static void main(String[] args) {

        TaskOddEven t1 = new TaskOddEven("Odd Thread : ", 1);
        TaskOddEven t2 = new TaskOddEven("Even Thread : ", 2);

        t1.start();
        t2.start();
    }
}

Output :-
Odd Thread : 1
Odd Thread : 3
Odd Thread : 5
Odd Thread : 7
Even Thread : 2
Even Thread : 4
Even Thread : 6
Even Thread : 8

Difference Between start() and run() in Java

The main difference is that start() creates a new thread of execution, whereas calling run() directly executes like a normal method on the current thread.

start() Method :
Java starts a new thread, and that new thread executes the run() method.

				
					class MyThread extends Thread {

    @Override
    public void run() {
        System.out.println("Running: " + Thread.currentThread().getName());
    }
}

public class Test {
    public static void main(String[] args) {

        MyThread t1 = new MyThread();
        t1.start();
    }
}

run() Method :
Java does not start a new thread. The run() method executes like a regular method on the current thread.

				
					MyThread t1 = new MyThread();
t1.run();

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