How to Create Threads in Java

There are two primary ways to create new threads in Java. The first, and more common, approach is to implement the Runnable interface. If you examine the Thread class’s source code, you’ll see that a Thread essentially calls the run() method on a Runnable object. The second method, which can be simpler in some cases, involves extending the Thread class directly and overriding its run() method.

Using Runnable

When using the Runnable interface, you typically create an anonymous inner class (or a separate class) that implements Runnable, and then pass an instance of it to the Thread constructor.

Thread secondMethod = new Thread(new Runnable() {
    int index = 0;
    @Override
    public void run() {
        try {
            while (index < 100) {
                int interval = (int) ((Math.random() * 500) + 500);
                Thread.sleep(interval);
                System.out.print("*");
                index++;
            }
        } catch (InterruptedException exc) {
            // Thread was interrupted; handle gracefully if needed.
        }
    }
});

Without Runnable (Extending Thread)

Alternatively, you can create a new thread by extending the Thread class itself and overriding its run() method. This approach can be more concise for simple thread implementations.

Thread firstMethod = new Thread() {
    int index = 0;
    @Override
    public void run() {
        try {
            while (index < 100) {
                int interval = (int) ((Math.random() * 500) + 500);
                sleep(interval); // 'sleep' can be called directly as this is a Thread instance
                System.out.print(".");
                index++;
            }
        } catch (InterruptedException exc) {
            // Thread was interrupted; handle gracefully if needed.
        }
    }
};

Using Runnable

Without Runnable (Extending Thread)

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