What is Runnable interface in Java?

Java runnable is an interface used to execute code on a concurrent thread. It is an interface which is implemented by any class if we want that the instances of that class should be executed by a thread.

public class ExampleClass implements Runnable {

@Override  
public void run() {  
    System.out.println("Thread has ended");  
}  
public static void main(String[] args) {  
    ExampleClass ex = new ExampleClass();  
    Thread t1= new Thread(ex);  
    t1.start();  
    System.out.println("Hi");  
}  

}

The runnable interface must be implemented by any class, whose instances are intended to be executed by a thread. The Runnable interface has only one run() method.

public void run()

This method is used to perform an action for a thread.

For a detailed tutorial on Java MultiThreading, visit
https://www.c-sharpcorner.com/article/a-complete-multithreading-tutorial-in-java/