- Thread is a block of code which can execute concurrently with other threads in the JVM. You can create and run a thread in either ways; Extending Thread class, Implementing Runnable interface.
- Both approaches do the same job but there have been some differences. Almost everyone have this question in their minds: which one is best to use? We will see the answer at the end of this post.
The most common difference is
- When you extends Thread class, after that you can’t extend any other class which you required. (As you know, Java does not allow inheriting more than one class).
- When you implements Runnable, you can save a space for your class to extend any other class in future or now.
However, the significant difference is.
- When you extends Thread class, each of your thread creates unique object and associate with it.
- When you implements Runnable, it shares the same object to multiple threads.
class ImplementsRunnable implements Runnable {
private int counter = 0;
public void run() {
counter++;
System.out.println("ImplementsRunnable : Counter : " + counter);
}
}
class ExtendsThread extends Thread {
private int counter = 0;
public void run() {
counter++;
System.out.println("ExtendsThread : Counter : " + counter);
}
}
public class ThreadVsRunnable {
public static void main(String args[]) throws Exception {
//Multiple threads share the same object.
ImplementsRunnable rc = new ImplementsRunnable();
Thread t1 = new Thread(rc);
t1.start();
Thread.sleep(1000); // Waiting for 1 second before starting next thread
Thread t2 = new Thread(rc);
t2.start();
Thread.sleep(1000); // Waiting for 1 second before starting next thread
Thread t3 = new Thread(rc);
t3.start();
//Creating new instance for every thread access.
ExtendsThread tc1 = new ExtendsThread();
tc1.start();
Thread.sleep(1000); // Waiting for 1 second before starting next thread
ExtendsThread tc2 = new ExtendsThread();
tc2.start();
Thread.sleep(1000); // Waiting for 1 second before starting next thread
ExtendsThread tc3 = new ExtendsThread();
tc3.start();
}
}
Output of the above program.
ImplementsRunnable : Counter : 1
ImplementsRunnable : Counter : 2
ImplementsRunnable : Counter : 3
ExtendsThread : Counter : 1
ExtendsThread : Counter : 1
ExtendsThread : Counter : 1
