ReentrantLock Condition

package com.company.bingfa;

import org.omg.PortableServer.THREAD_POLICY_ID;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.ReentrantLock;

class MyService{
    ReentrantLock reentrantLock = new ReentrantLock();
    Condition conditionA = reentrantLock.newCondition();
    Condition conditionB = reentrantLock.newCondition();

    public void waitA(){
        try{
            reentrantLock.lock();

            System.out.println("start A");

            conditionA.await();

            System.out.println("finish A");

        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            reentrantLock.unlock();
        }
    }

    public void waitB(){
        try{
            reentrantLock.lock();

            System.out.println("start B");

            conditionB.await();

            System.out.println("finish B");

        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            reentrantLock.unlock();
        }
    }

    public void signalA(){
        try{
            reentrantLock.lock();
            conditionA.signal();
        } finally {
            reentrantLock.unlock();
        }
    }

    public void signalB(){
        try{
            reentrantLock.lock();
            conditionB.signal();
        } finally {
            reentrantLock.unlock();
        }
    }

}

class ThreadAA extends Thread{
    private MyService service;

    public ThreadAA(MyService service) {
        this.service = service;
    }

    @Override
    public void run() {
        service.waitA();
    }
}

class ThreadBB extends Thread{
    private MyService service;

    public ThreadBB(MyService service) {
        this.service = service;
    }

    @Override
    public void run() {
        service.waitB();
    }
}

public class MyReentrantLock2 {
    public static void main(String[] args) throws InterruptedException {
        MyService service = new MyService();
        ThreadAA tA = new ThreadAA(service);
        ThreadBB tB = new ThreadBB(service);
        tA.start();
        tB.start();

        Thread.sleep(3000);
        service.signalA();
        Thread.sleep(5000);
        service.signalB();
    }
}