public interface ResponseCallBack {

    public void printMsg(String msg);

}

public class TestMain {

    public static void main(String[] args){

        ExecutorService executorService = Executors.newFixedThreadPool(1);

        executorService.submit(new TestThread(new ResponseCallBack() {

            @Override

            public void printMsg(String msg) {

                System.out.println("print message: " + msg);

            }

        }));

        executorService.shutdown();

    }

}

class TestThread implements Runnable {

    private ResponseCallBack responseCallBack;

    public TestThread(ResponseCallBack responseCallBack) {

        this.responseCallBack = responseCallBack;

    }

    @Override

    public void run() {

        try {

            System.out.println(Thread.currentThread().getName() + " start execute");

            Thread.sleep(3000);   // 耗时任务

            System.out.println(Thread.currentThread().getName() + " end execute");

            this.responseCallBack.printMsg("Hello Call Back");  // 耗时任务执行完后，通知主线程

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

    }

}