Java Reference
In-Depth Information
Explicitly Implementing the Runnable Interface
This is very similar to the technique described in the previous sub-section. With this
method, however, we fi rst create an application class that explicitly implements the
Runnable interface. Then, in order to create a thread, we instantiate an object of our
Runnable class and 'wrap' it in a Thread object. We do this by creating a Thread
object and passing the Runnable object as an argument to the Thread constructor.
(Recall that the Thread class has seven constructors.) There are two Thread con-
structors that allow us to do this:
￿ Thread (Runnable<object>)
￿ Thread(Runnable<object>, String<name>)
(The second of these allows us also to name the thread.)
When either of these constructors is used, the Thread object uses the run method of
the Runnable object in place of its own (empty) run method.
Once a Runnable object has been used as an argument in the Thread constructor,
we may never again need to refer to it. If this is the case, we can create such an object
anonymously and dynamically by using the operator new in the argument supplied to
the Thread constructor, as shown in the example below. However, some people may
prefer to create a named Runnable object fi rst and then pass that to the Thread
constructor, so the alternative code is also shown. The second method employs
about twice as much code as the fi rst, but might serve to make the process clearer.
Example (Same effect as that of ThreadShowName )
Note that, since the thread objects in this example are not of class Thread (since
RunnableShowName does not extend Thread ), they cannot make direct use of meth-
ods getName and sleep , but must go through class Thread to make use of static
methods currentThread and sleep . The former method is used to get a pointer to the
current thread, in order to use that pointer to call method getName .
public class RunnableShowName implements Runnable
public static void main(String[] args)
Thread thread1 =
new Thread(new RunnableShowName());
Thread thread2 =
new Thread(new RunnableShowName());
As an alternative to the above 2 lines, the following
(more long-winded) code could have been used:
RunnableShowName runnable1 =
new RunnableShowName();
RunnableShowName runnable2 =
new RunnableShowName();
Thread thread1 = new Thread(runnable1);
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