Start Two Threads at the Exact Same Time in Java

Start Two Threads at the Exact Same Time in Java

Threads are a great way for your program to run multiple tasks at once, but how do you start two threads at the exact same time in Java? Here we'll discuss how to use the threading construct of Java to do just that.

Creating Your Threads

The first step is to create your threads. This involves declaring and instantiating the threads, like so:

Thread t1 = new Thread();
Thread t2 = new Thread();

You can then set the code that each thread will execute, using the .run() method:

t1.run(() -> {
    // Code to be executed by thread 1
});

t2.run(() -> {
    // Code to be executed by thread 2
});

Starting the Threads

Once you have your threads defined, the next step is to start them. To do this, you can use the .start() method for each thread:

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

It's important to note that this does not guarantee that both threads will start at the exact same time. The .start() method only kicks off the process for each thread. It's up to the JVM to decide when and how to run each thread.

Synchronizing the Threads

In order to guarantee that both threads actually start executing at the same time, you need to synchronize them. This involves putting both threads into a synchronized block, like so:

synchronized (this) {
    t1.start();
    t2.start();
}

This ensures that both threads will actually start at the same time. It's worth mentioning that while this technique works, it should be used sparingly, as too much synchronization can lead to poor performance.

Conclusion

In this tutorial, we discussed how to start two threads at the exact same time in Java. We looked at creating the threads and synchonizing them to ensure simultaneous execution. We also discussed the importance of only using this technique when necessary due to the potential performance problems it can cause.