isCancelled(): Cancellation status

boolean isCancelled()

Returns true if this task was cancelled before it completed normally.

Example

import java.util.concurrent.*;
import java.util.*;

public class CallableTask implements Callable{
 String name;

 CallableTask(String name){
  this.name = name;
 }

 public String call(){
  try{
   System.out.println(name +" Started Executing");
   Thread.sleep(1000);
   System.out.println(name +" Finishes Execution");
  }
  catch(Exception e){
   System.out.println("Task Interrupted " + e);
  }
  return (new Date() + " :: " + name);
 }
}

   

import java.util.concurrent.*;
import java.util.*;

class SimpleThreadPool{
 public static void main(String args[])throws Exception{
  List<Future<String>> l1 = new ArrayList<Future<String>> ();
  ExecutorService exec = new ThreadPoolExecutor(3, 3, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>());

  CallableTask task1 = new CallableTask("task1");

  Future<String> f1 = exec.submit(task1);
  Future<String> f2 = exec.submit(task1);

  f1.cancel(false);
  f2.cancel(true);

  System.out.println("is the task cancelled " + f1.isCancelled());
  System.out.println("is the task cancelled " + f2.isCancelled());
  exec.shutdown();
 }
}

Output

task1 Started Executing
task1 Started Executing
is the task cancelled true
is the task cancelled true
Task Interrupted java.lang.InterruptedException: sleep interrupted
task1 Finishes Execution

As you observe the output, task1 finishes execution normally, where as task2 thrown InterruptedException. Since f1 calls cancel with false as argument and f2 calls cancel with true as an argument.

f1.cancel(false)

f2.cancel(true)

ExecutorService exec = new ThreadPoolExecutor(3, 3, 0L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>())

Statement creates a thread pool of 3 threads.

exec.submit(tasks)

Submit the tasks to the thread pool. When the task is submitted, ThreadPool assigns a thread to execute the call method of the Callable Object.

Check completion status of the task                                                 ExecutorService interface                                                 Home