20.19 The Interface java.lang.Runnable
Runnable interface should be implemented by any class whose instances are
intended to be executed by a new thread. All that is required of such a class is that
it implement a method of no arguments called
public abstract void run()
If an object implementing interface
Runnable is used to create a thread (§20.20), then starting the thread will (normally) lead to the invocation of the object's
run method in that separately executing thread.