Java FutureTask Example
November 16, 2023
java.util.concurrent.FutureTask is introduced in Java 5 and is the part of executor framework.
2.
FutureTask allows canceling the task by its cancel() method.
3.
FutureTask implements the Future interface and its object is created by passing the object of the class which implements Callable.
4. If before calling the
run method of FutureTask, task is cancelled, then on calling run method, it will not allow running the thread.
Example-1
FutureTaskTest.java
package com.concretepage;
import java.util.concurrent.Callable;
import java.util.concurrent.FutureTask;
public class FutureTaskTest {
public static void main(String... args){
FutureTask<String> ft= new FutureTask<String>(new DemoTask());
boolean b=ft.cancel(true);
ft.run();
System.out.println(b);
}
}
class DemoTask implements Callable<String>{
public String call() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
System.out.println(e);
}
return "Task Done";
}
}
DemoThread which implements Callable interface. Now we have created an object of FutureTask. We call the cancel method. And then call the run method. We can see that now the thread will not run.
Example-2
Find another example that completes its task and uses different method ofFutureTask to check the task health.
FutureTaskDemo.java
package com.concretepage;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.FutureTask;
public class FutureTaskDemo {
public static void main(String... args) throws InterruptedException, ExecutionException {
ExecutorService exService = Executors.newSingleThreadExecutor();
FutureTask<String> futureTask= new FutureTask<String>(new Task());
exService.execute(futureTask);
//checks if task done
System.out.println(futureTask.isDone());
//checks if task canceled
System.out.println(futureTask.isCancelled());
//fetches result and waits if not ready
System.out.println(futureTask.get());
}
}
class Task implements Callable<String>{
public String call() {
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
System.out.println(e);
}
return "Task Done";
}
}
false false Task Done
