Lock基本使用

1. Lock lock = new ReentrantLock(); 创建一个lock对象，在lock.lock() 与 lock.unLock() 之间的部分互斥执行，类似于synchronize。例一
2. Condition conditionA = lock.newCondition(); 创建一个Condition对象，可以使用await() 方法和signal()方法，可使用一个condition对象创建多个Condition对象，达到线程组的等待和唤醒操作。在调用lock.await()或者lock.signal()前要进行lock.lock()。例二
3. 经典问题消费者生产者问题，多个线程使用signal可能导致假死，与synchronize相同，可以使用signalAll方式解决。可以用conditionP和conditionC进行等待/唤醒。例三

例一：

import javax.sound.midi.Soundbank;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;// lock使用： 在lock() 与 unlock() 之间代码执行互斥 与 synchronize类似
// 使用Condition condition = lock.newCondition() 实现等待/通知
// 使用 condition.await() 或者 condition.signal() 之前要先使用lock()加锁 也可以使用signalAll() 释放掉所有await()
class Service01 {private Lock lock = new ReentrantLock();private Condition condition = lock.newCondition();public void await() {try {lock.lock();System.out.println("await时间为：" + System.currentTimeMillis());condition.await();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}public void signal() {try {lock.lock();System.out.println("signal的时间为：" + System.currentTimeMillis());condition.signal();} finally {lock.unlock();}}public void signalAll() {try {lock.lock();System.out.println("signalAA 执行时间：" + System.currentTimeMillis());condition.signalAll();} finally {lock.unlock();}}
}class ThreadA extends Thread {private Service01 service01;public ThreadA(Service01 service01) {this.service01 = service01;}@Overridepublic void run() {service01.await();}
}public class StudyThreads01Lock基本用法 {public static void main(String[] args) throws InterruptedException {Service01 service01 = new Service01();ThreadA threadA = new ThreadA(service01);threadA.start();Thread.sleep(2000);service01.signal();System.out.println("========================");Service01 service02 = new Service01();ThreadA threadA1 = new ThreadA(service02);ThreadA threadA2 = new ThreadA(service02);ThreadA threadA3 = new ThreadA(service02);ThreadA threadA4 = new ThreadA(service02);ThreadA threadA5 = new ThreadA(service02);threadA1.start();threadA2.start();threadA3.start();threadA4.start();threadA5.start();Thread.sleep(5000);service02.signalAll();}
}

例二：

package com.chapter04;import java.util.Date;
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;class Service02 {private Lock lock = new ReentrantLock();private Condition conditionA = lock.newCondition();private Condition conditionB = lock.newCondition();public void awaitA() {try {lock.lock();System.out.println("awaitA 开始时间：" + new Date());conditionA.await();System.out.println("awaitA 结束时间：" + new Date());} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}public void awaitB() {try {lock.lock();System.out.println("awaitB 开始时间：" + new Date());conditionB.await();System.out.println("awaitB 结束时间：" + new Date());} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}public void signalAllA() {try {lock.lock();System.out.println("signalAllA 时间：" + new Date());conditionA.signalAll();} finally {lock.unlock();}}public void signalAllB() {try {lock.lock();System.out.println("signalB时间：" + new Date());conditionB.signalAll();} finally {lock.unlock();}}
}class ThreadA02 extends Thread {private Service02 service02;public ThreadA02(Service02 service02) {this.service02 = service02;}@Overridepublic void run() {service02.awaitA();}
}class ThreadB02 extends Thread {private Service02 service02;public ThreadB02(Service02 service02) {this.service02 = service02;}@Overridepublic void run() {service02.awaitB();}
}public class StudyThreads02使用Condition实现线程分组唤醒 {public static void main(String[] args) throws InterruptedException {Service02 service02 = new Service02();ThreadA02 threadA02_1 = new ThreadA02(service02);ThreadA02 threadA02_2 = new ThreadA02(service02);ThreadA02 threadA02_3 = new ThreadA02(service02);ThreadA02 threadA02_4 = new ThreadA02(service02);ThreadB02 threadB02_1 = new ThreadB02(service02);ThreadB02 threadB02_2 = new ThreadB02(service02);ThreadB02 threadB02_3 = new ThreadB02(service02);ThreadB02 threadB02_4 = new ThreadB02(service02);threadA02_1.start();threadA02_2.start();threadA02_3.start();threadA02_4.start();threadB02_1.start();threadB02_2.start();threadB02_3.start();threadB02_4.start();Thread.sleep(5000);service02.signalAllA();}
}

例三：

package com.chapter04;import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;class MyService03 {private Lock lock = new ReentrantLock();private Condition conditionP = lock.newCondition();private Condition conditionC = lock.newCondition();private Condition condition = lock.newCondition();volatile private boolean hasValue = true;public void P() {try {lock.lock();while (hasValue) {System.out.println("进入生产者,此时有产品需要等待：" + hasValue);// 有产品 生产者等待conditionP.await();}System.out.println(Thread.currentThread().getName() + "=== 生产者-- 生产 --了一个产品");hasValue = true;System.out.println("结束生产者,此时：" + hasValue);// 生产了一个产品，唤醒消费者conditionC.signalAll();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}public void C() {try {lock.lock();while (!hasValue) {System.out.println("进入消费者,此时无产品需要等待：" + hasValue);// 此时无产品，消费者需要等待conditionC.await();}System.out.println(Thread.currentThread().getName() + "=== 消费者-- 消费 --了一个产品");hasValue = false;System.out.println("结束消费者,此时：" + hasValue);// 消费了一个产品，唤醒生产者进行生产conditionP.signalAll();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}
}class ThreadP03 extends Thread {private MyService03 myService03;public ThreadP03(MyService03 myService03) {this.myService03 = myService03;}@Overridepublic void run() {for (int i = 0; i < 10; i++) {myService03.P();}}
}class ThreadC03 extends Thread {private MyService03 myService03;public ThreadC03(MyService03 myService03) {this.myService03 = myService03;}@Overridepublic void run() {for (int i = 0; i < 10; i++) {myService03.C();}}
}public class StudyThreads03生产者消费者在Lock中的使用 {public static void main(String[] args) {MyService03 service03 = new MyService03();ThreadP03[] threadP03s = new ThreadP03[10];ThreadC03[] threadC03s = new ThreadC03[10];for (int i = 0; i < 10; i++) {threadC03s[i] = new ThreadC03(service03);threadP03s[i] = new ThreadP03(service03);threadC03s[i].start();threadP03s[i].start();}}
}