How can you run a block of code in a different thread instead of the main thread in Java?

In Java, to run a piece of code in a different thread instead of the main one, you can use the Thread class or the Runnable interface. Classes from java.util.concurrent, such as ExecutorService, are also commonly used.

Example using Thread:

public class Main {
    public static void main(String[] args) {
        Thread thread = new Thread(new Runnable() {
            @Override
            public void run() {
                System.out.println("Code is running in another thread");
            }
        });
        thread.start(); // Starting a new thread
    }
}

Or using a lambda expression (Java 8+):

new Thread(() -> {
    System.out.println("Code is running in another thread");
}).start();

If you need to manage a thread pool, it's better to use ExecutorService:

ExecutorService executor = Executors.newSingleThreadExecutor();
executor.submit(() -> {
    System.out.println("Executing in another thread via ExecutorService");
});
executor.shutdown();

Thus, the code that needs to run in another thread is placed in a Runnable or Callable and started via a new thread or a thread pool.