Running threads using Executors

There are several ways of running threads.
We can create an instance of Runnable and pass it to Thread class:

	Runnable runnable = new Runnable() {
	@Override
	public void run() {
	System.out.println("thread 1");
	}
	};
	Thread thread1 = new Thread(runnable);
	thread1.start();

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Or we can override the run() method in the Thread class directly:

	Thread thread2 = new Thread() {
	@Override
	public void run() {
	System.out.println("thread 2");
	}
	};
	thread2.start();

view raw ThreadCreationOverriding.java hosted with ❤ by GitHub

However the better solution (in most cases) is using the Executor interface.
It gives us a couple of benefits. In previous cases, if we want to start again the thread that has come to the terminated state we will get IllegalThreadStateException.
With Executor we can reuse the existing Runnable :

	ExecutorService executor = Executors.newSingleThreadExecutor();
	Runnable runnable = new Runnable() {
	@Override
	public void run() {
	System.out.println(Thread.currentThread().getName());
	}
	};
	executor.execute(runnable);
	// executing once again
	executor.execute(runnable);
	executor.shutdown();

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To prevent adding any more tasks to our executor we need to call shutdown() method.

What is even more important, it provides the ability to easily switch the implementation of running: using single thread, different kinds of thread pools or even scheduled periodic task.
We would just need to use different static factory method from Executors utility class:

	ExecutorService executor = Executors.newFixedThreadPool(2);
	Runnable runnable = new Runnable() {
	@Override
	public void run() {
	System.out.println(Thread.currentThread().getName());
	}
	};
	executor.execute(runnable);
	executor.execute(runnable);
	executor.shutdown();

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This time our runnable is run using two threads from executor's thread pool.