Fix Settings creating too many threads unexpectedly

import android.os.Handler;

import android.os.Looper;

import java.util.concurrent.Callable;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.Future;

    private static volatile Thread sMainThread;

    private static volatile Handler sMainThreadHandler;

    private static volatile ExecutorService sSingleThreadExecutor;

    private static volatile ExecutorService sThreadExecutor;

    /**

     * Returns true if the current thread is the UI thread.

     * @Return A future of the task that can be monitored for updates or cancelled.

     */

    public static Future postOnBackgroundThread(Runnable runnable) {

        if (sSingleThreadExecutor == null) {

            sSingleThreadExecutor = Executors.newSingleThreadExecutor();

        return getThreadExecutor().submit(runnable);

    }

        return sSingleThreadExecutor.submit(runnable);

    /**

     * Posts callable in background using shared background thread pool.

     *

     * @Return A future of the task that can be monitored for updates or cancelled.

     */

    public static Future postOnBackgroundThread(Callable callable) {

        return getThreadExecutor().submit(callable);

    }

    /**

        getUiThreadHandler().post(runnable);

    }

    private static synchronized ExecutorService getThreadExecutor() {

        if (sThreadExecutor == null) {

            sThreadExecutor = Executors.newFixedThreadPool(

                    Runtime.getRuntime().availableProcessors());

        }

        return sThreadExecutor;

    }

}

    }

    @Test

    public void testPostOnMainThread_shouldRunOnMainTread() {

    public void testPostOnMainThread_shouldRunOnMainThread() {

        TestRunnable cr = new TestRunnable();

        ShadowLooper.pauseMainLooper();

        ThreadUtils.postOnMainThread(cr);