ExecutorService which runs tasks in calling thread?

Question

Are there any java.util.ExecutorService implementations which simply run all executed tasks in the calling thread? If this isn't included in Java by default, is there a library which contains an implementation like this?

Answer 1

The only existing implementation I could find is SynchronousExecutorService - unfortunately buried somewhere in camel library.

Pasting source code (without comments) here for future reference:

package org.apache.camel.util.concurrent;

import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.TimeUnit;

public class SynchronousExecutorService extends AbstractExecutorService {

    private volatile boolean shutdown;

    public void shutdown() {
        shutdown = true;
    }

    public List<Runnable> shutdownNow() {
        return null;
    }

    public boolean isShutdown() {
        return shutdown;
    }

    public boolean isTerminated() {
        return shutdown;
    }

    public boolean awaitTermination(long time, TimeUnit unit) throws InterruptedException {
        return true;
    }

    public void execute(Runnable runnable) {
        runnable.run();
    }

}

Answer 2

You may use Guava com.google.common.util.concurrent.MoreExecutors.sameThreadExecutor() which does exactly what you want: https://github.com/google/guava/blob/0434c5199c83c3f43b8b6a86c62e121d518fe7d0/guava/src/com/google/common/util/concurrent/MoreExecutors.java#L267

EDIT: The method has been renamed to com.google.common.util.concurrent.MoreExecutors.newDirectExecutorService() https://github.com/google/guava/blob/f67ab864bde63fa6602b5688de0440957ffeaa2e/guava/src/com/google/common/util/concurrent/MoreExecutors.java#L369

Answer 3

have you looked at java.util.concurrent.ThreadPoolExecutor?