4.5.2 Java Threads and the Runnable Interface

There is a Thread class in the java.lang package. To write code that will be executed as a separate thread, there are two possibilities. Either

1. Extend Thread in your class and override the void run() method with the code you wish the thread to run.
2. Or write a class which implements the Runnable interface, which requires the class to have a void run() method. Then to generate a thread, an instance of the class implementing Runnable is passed as an argument in the constructor for a new Thread eg

   class Bar implements Runnable {
        ...
       public void run() {
         // do what you want
       }
       ...
   }
   
       ...
       Thread foo = new Thread(new Bar());
       foo.start();
       ...
   

The second approach is the preferred way. Why?

Having created the thread, call void start() on the thread object to hand the thread into the VM scheduler, which then invokes the run method.