ExecutorCompletionService in Java
November 15, 2023
ExecutorCompletionService is the implementaion of CompletionService interface. It has take() that returns only those those threads which has completed its task. The Callable threads submitted to ExecutorCompletionService, can be obtained using take() method after their task completion.
Example
package com.concretepage;
import java.util.concurrent.Callable;
import java.util.concurrent.CompletionService;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorCompletionService;
import java.util.concurrent.Executors;
public class ExecutorCompletionServiceTest {
public static void main(String... args) throws InterruptedException, ExecutionException{
Executor ex= Executors.newCachedThreadPool();
CompletionService<Long> cs = new ExecutorCompletionService<Long>(ex);
cs.submit(new Worker());
cs.submit(new Worker());
cs.submit(new Worker());
for(int i=0;i<3;i++){
long l=cs.take().get();
//utilize the result
System.out.println(l);
}
}
}
class Worker implements Callable{
@Override
public Long call() throws Exception {
//do some task and return back
return System.currentTimeMillis();
}
}
ExecutorCompletionService object. The role of ExecutorCompletionService is that when we try to get retuned value of thread, ExecutorCompletionService will return the value only of those threads which has completed its task.
