31 August 2016

callback on thread completion

The code illustrate how callback is being accomplished on Thread completion:


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class Executor {

  public <T> void execute(Callable<T> task, BiConsumer<T, ? super Exception> callback) {
     CallableThread<T> thread = new CallableThread<>(task, callback);
     thread.start();
  }

  class CallableThread<T> extends Thread {

     Callable<T> task;
     BiConsumer<T, ? super Exception> callback;

     public CallableThread(Callable<T> task, BiConsumer<T, ? super Exception> callback) {
        this.task = task;
        this.callback = callback;
     }

     public void run() {
        System.out.println("running task on thread : " + Thread.currentThread().getName());
        try {
            T t = task.call();
            callback.accept(t, null);
        } catch (Exception ex) {
            callback.accept(null, ex);
        }
     }
   }
 }

Caller:
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System.out.println("running task on thread : " + Thread.currentThread().getName());

new Executor().execute(() -> "HELLO WORKD", (result, ex) -> {
    System.out.println("result: " + result);
    System.out.println("exception: " + ex);
});

System.out.println("finished running task on thread : " + Thread.currentThread().getName());


Output:
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running task on thread : main
finished running task on thread : main
running task on thread : Thread-0
result: HELLO WORKD
exception: null

It appears that, the Executor is submitting the Callable to execution and on complete it invokes the callback functional interface.


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