Java Never Ends - Java - page 1036

The Thread Class
A thread is an object of the class Thread . The normal way to program a thread is to define a
class that is a derived class of the class Thread . An object of this derived class will be a
thread that follows the programming given in the definition of the derived (thread) class's
method named run .
Any thread class inherits the method start from the class Thread . An invocation of start
by an object of a thread class will start the thread and invoke the method run for that thread.
See Display 19.2 for an example.
The Runnable Interface ★
There are times when you would rather not make a thread class a derived class of the
class Thread . The alternative to making your class a derived class of the class Thread is
to have your class instead implement the Runnable interface. The Runnable interface
has only one method heading:
public void run()
A class that implements the Runnable interface must still be run from an instance of
the class Thread . This is usually done by passing the Runnable object as an argument
to the thread constructor. The following is an outline of one way to do this:
public class ClassToRun extends SomeClass implements Runnable
{
....
public void run()
{
//Fill this just as you would if ClassToRun
//were derived from Thread.
}
....
public void startThread()
{
Thread theThread = new Thread( this );
theThread.run();
}
....
}
The above method startThread is not compulsory, but it is one way to produce a
thread that will in turn run the run method of an object of the class ClassToRun . In
Display 19.3 we have rewritten the program in Display 19.2 using the Runnable inter-
face. The program behaves exactly the same as the one in Display 19.2.