Creating and Starting Java Threads: Subclassing Thread and Implementing Runnable

Java thread objects are instances of java.lang.Thread or its subclasses. A thread can be created with Thread thread = new Thread(); and started by invoking thread.start(); , which triggers the thread's run() method.

Two main ways exist to provide code for a thread: extending the Thread class and overriding run() , or creating a class that implements the Runnable interface and passing its instance to a Thread constructor.

Creating a Thread subclass

public class MyThread extends Thread {
    public void run() {
        System.out.println("MyThread running");
    }
}

MyThread myThread = new MyThread();
myThread.start();

An anonymous subclass can also be used:

Thread thread = new Thread() {
    public void run() {
        System.out.println("Thread Running");
    }
};
thread.start();

Implementing Runnable

public class MyRunnable implements Runnable {
    public void run() {
        System.out.println("MyRunnable running");
    }
}

Thread thread = new Thread(new MyRunnable());
thread.start();

An anonymous Runnable can be created similarly:

Runnable myRunnable = new Runnable() {
    public void run() {
        System.out.println("Runnable running");
    }
};
Thread thread = new Thread(myRunnable);
thread.start();

Common mistake: calling run() directly instead of start() . Doing so executes the method in the current thread rather than creating a new concurrent thread.

Thread newThread = new Thread(new MyRunnable());
newThread.run(); // should be newThread.start();

Threads can be named to aid debugging:

Thread thread = new Thread(runnable, "New Thread");
thread.start();
System.out.println(thread.getName());

The current thread's name can be obtained with:

String threadName = Thread.currentThread().getName();

Example showing multiple threads with custom names:

public class ThreadExample {
    public static void main(String[] args) {
        System.out.println(Thread.currentThread().getName());
        for (int i = 0; i < 10; i++) {
            new Thread("" + i) {
                public void run() {
                    System.out.println("Thread: " + getName() + " running");
                }
            }.start();
        }
    }
}

Note that thread start order does not guarantee execution order; the operating system scheduler determines which thread runs first.

Original source: http://ifeve.com/creating-and-starting-java-threads/

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