Helper class of ExecutorService for Android

AppExecutors.java

/*
 * Copyright (C) 2014 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

import android.os.Handler;
import android.os.Looper;
import android.support.annotation.NonNull;

import java.util.concurrent.Executor;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class AppExecutors {

    private static final Object LOCK = new Object();
    private static AppExecutors sInstance;
    
    private final ExecutorService diskIO;
    private final ExecutorService networkIO;
    private final Executor mainThread;

    private AppExecutors(ExecutorService diskIO, ExecutorService networkIO, Executor mainThread) {
        this.diskIO = diskIO;
        this.networkIO = networkIO;
        this.mainThread = mainThread;
    }

    /* Singletone pattern? The pattern depends on the developer */
    public static AppExecutors getInstance() {
        if (sInstance == null) {
            synchronized (LOCK) {
                if (sInstance == null) {
                    sInstance = new AppExecutors(Executors.newSingleThreadExecutor(),
                        Executors.newFixedThreadPool(3),
                        new MainThreadExecutor());
                }
            }
        }
        return sInstance;
    }

    public ExecutorService diskIO() {
        return diskIO;
    }

    public ExecutorService networkIO() {
        return networkIO;
    }
    
    public Executor mainThread() {
        return mainThread;
    }

    private static class MainThreadExecutor implements Executor {
        private Handler mainThreadHandler = new Handler(Looper.getMainLooper());

        @Override
        public void execute(@NonNull Runnable command) {
            mainThreadHandler.post(command);
        }
    }

}