Activity.java

new MyCustomAsyncTask().executeOnExecutor(ExecutorManager.getInstance().getExecutor())

ExecutorManager.java

import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

public class ExecutorManager {
    private static volatile ExecutorManager sSoleInstance;
    private ExecutorService executor;
    private ThreadPoolExecutor threadPoolExecutor;

    public static ExecutorManager getInstance() {
        if (sSoleInstance == null) {
            synchronized (ExecutorManager.class) {
                if (sSoleInstance == null) {
                    sSoleInstance = new ExecutorManager();
                }
            }
        }

        return sSoleInstance;
    }

    private ExecutorManager() {
        if (sSoleInstance != null) {
            throw new RuntimeException("Use getInstance() method to get the single instance of this class.");
        }
    }

    public ExecutorService getExecutor() {
        if (executor == null) {
            int NUMBER_OF_CORES = Runtime.getRuntime().availableProcessors();
            int KEEP_ALIVE_TIME = 1;
            TimeUnit KEEP_ALIVE_TIME_UNIT = TimeUnit.MINUTES;

            int maxWorkCount = 1_000;
//            int coreAmount = 8;
//            int overrun = 4;
//            executor = new ThreadPoolExecutor(coreAmount, coreAmount + overrun, 1, TimeUnit.MINUTES, new ArrayBlockingQueue<Runnable>(maxWorkCount));
            threadPoolExecutor = new ThreadPoolExecutor(NUMBER_OF_CORES * 5,
                    NUMBER_OF_CORES * 5,
                    KEEP_ALIVE_TIME,
                    KEEP_ALIVE_TIME_UNIT,
                    new ArrayBlockingQueue<Runnable>(maxWorkCount));
            executor = threadPoolExecutor;
        }
        return executor;
    }

    public int getActiveThreadCount() {
        if (threadPoolExecutor != null) {
            return threadPoolExecutor.getActiveCount();
        }
        return -1;
    }
}