17.4 Thread Definition

There are two ways to define threads. One way is to define a class that inherits class Thread; another way is to define a class that implements the Runnable interface. The first way to use threads is to derive a subclass from the Thread class and override the run() method. The following is a simple portion of code that illustrates the first method:

       description          This class defines a thread. */       class MyThread inherits Thread is       public       description         This is the main body of the thread definition.         */       void function run is              //              // do something;              // When this method returns,              // the thread terminates       endfun run       endclass MyThread

To create a thread and start its execution, the following portion of code is included in the main class of an application program:

       objects          object mt of class MyThread          ...       begin          ...          create mt of class MyThread          call start of mt    // start running the thread          ...

The second technique to define a class that implements the Runnable interface and override the run() method. The following is a simple portion of code that illustrates this thechnique:

       description         This class also defines a thread. */       class MyThreadb inherits OtherClass                                 implements Runnable is       public       description          This is the main body of the thread definition.          */       void function run is               //               // do something;               // When this method returns,               // the thread terminates       endfun run       endclass MyThreadb

The advantage of the second technique is that there is no need to inherit class Thread. To create a thread and start its execution, the following portion of code is included in the main class of an application program:

       objects         object ms of class MyThreadb         object myth of class Thread         ...       begin         ...         create ms of class MyThreadb         create myth of class Thread using ms         call start of myth