Java多線程Lock

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JDK5以後為代碼的同步提供了更加靈活的Lock+Condition模式，並且一個Lock可以綁定多個Condition對象

1.把原來的使用synchronized修飾或者封裝的代碼塊用lock.lock()與lock.unlock()進行手動的鎖擷取與釋放

//原來的同步方式synchronized (obj) {...}//JDK5.0新增的同步方式//lock.unlock();建議最好要放在finally 執行try {lock.lock();...} finally {lock.unlock();}

2.把原來線程之間的通訊方式由鎖對線obj.wait()和obj.notify()改成了Condition對象的con.await()與con.signal()方法

如下用Lock的方式重寫多生產者多消費者模式時，線程可以指定喚醒生產者或者消費者，這樣擁有更高的效率與安全性

 

package jdk5lockDome;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;/** * @author wpy *  */public class ProducerConsumer {public static void main(String[] args) {Resource resource = new Resource();Producer producer0 = new Producer(resource);Producer producer1 = new Producer(resource);Consumer consumer2 = new Consumer(resource);Consumer consumer3 = new Consumer(resource);Thread t0 = new Thread(producer0);Thread t1 = new Thread(producer1);Thread t2 = new Thread(consumer2);Thread t3 = new Thread(consumer3);t0.start();t1.start();t2.start();t3.start();}}class Producer implements Runnable {private Resource resource;public Producer(Resource resource) {this.resource = resource;}@Overridepublic void run() {while (true) {resource.set("資源");}}}class Consumer implements Runnable {private Resource resource;public Consumer(Resource resource) {this.resource = resource;}@Overridepublic void run() {while (true) {resource.out();}}}class Resource {private String name;private int count = 1;// 是否產生完畢private boolean flag = false;/** * 互斥鎖（同時只有一個線程擁有鎖） */private Lock lock = new ReentrantLock();private Condition producerCon = lock.newCondition();private Condition consumerCon = lock.newCondition();/** * 生產方法 *  * @param name */public void set(String name) {try {lock.lock();String threadName = Thread.currentThread().getName();while (flag) {System.out.println(threadName + "進入等待狀態");producerCon.await();}System.out.println(threadName + "取得執行權");this.name = name + count;count++;System.out.println("生產者：" + this.name);flag = true;consumerCon.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}/** * 消費方法 */public void out() {try {lock.lock();String threadName = Thread.currentThread().getName();while (!flag) {System.out.println(threadName + "進入等待狀態");consumerCon.await();}System.out.println(threadName + "取得執行權");System.out.println("============消費者：" + name);flag = false;producerCon.signal();} catch (InterruptedException e) {e.printStackTrace();} finally {lock.unlock();}}}

　　

　　

Java多線程Lock