Java并发编程-Condition使用实例
本文将简单介绍用于线程协作的Condition, 并给出一个例子，实现一个多线程题目--有三个线程分别打印A、B、C,请用多线程编程实现，在屏幕上循环打印10次ABCABC…
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Condition是从JDK 1.5开始有的。API是这么描述的：
以上是Condition接口定义的方法，await()对应于Object#wait()，signal()对应于Object#notify()，signalAll()对应于Object#notifyAll()。
Condition是与Lock结合使用的，通过Lock.newCondition()方法能够创建与Lock绑定的Condition实例。
Lock和Condition的关系就如同 Object.wait(),Object.notify()方法和synchronized一样，它们都可以配合使用完成对多线程协作的控制。
JDK提供的ArrayBlockingQueue很好地诠释了Condition的使用。
package my.thread.test;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;import java.util.logging.Logger;/** * 题目：有三个线程分别打印A、B、C,请用多线程编程实现，在屏幕上循环打印10次ABCABC… * * 本程序采用Lock和Condition来实现。 * * @author Eric * */public class ConditionExample {private Lock lock = new ReentrantLock();private Condition conditionA = lock.newCondition();private Condition conditionB = lock.newCondition();private Condition conditionC = lock.newCondition();/** 当前线程的名字 */private char currentThreadName = 'A';private static final Logger logger = Logger.getLogger("my.thread.test.OrderPrintTest");public static void main(String[] args) {ConditionExample ce = new ConditionExample();ExecutorService service = Executors.newFixedThreadPool(3);service.execute(ce.new ThreadA());service.execute(ce.new ThreadB());service.execute(ce.new ThreadC());service.shutdown();}private class ThreadA implements Runnable {public void run() {for (int i = 0; i < 10; i++) {lock.lock();try {while (currentThreadName != 'A') {try {/* * 如果当前线程名字不是A，那么ThreadA就处理等待状态 */conditionA.await();} catch (InterruptedException e) {logger.severe(e.getLocalizedMessage());}}/* * 打印出第几遍以及A信息 */System.out.println(String.format("第%d遍", i + 1));System.out.println("A");/* * 将当前线程名置为B， 然后通知ThreadB执行 */currentThreadName = 'B';conditionB.signal();} finally {lock.unlock();}}}}private class ThreadB implements Runnable {public void run() {for (int i = 0; i < 10; i++) {lock.lock();try {while (currentThreadName != 'B') {try {/* * 如果当前线程名字不是B，那么ThreadB就处理等待状态 */conditionB.await();} catch (InterruptedException e) {logger.severe(e.getLocalizedMessage());}}/* * 打印信息B */System.out.println("B");/* * 将当前线程值置为C 并通过ThreadC来执行 */currentThreadName = 'C';conditionC.signal();} finally {lock.unlock();}}}}private class ThreadC implements Runnable {public void run() {for (int i = 0; i < 10; i++) {lock.lock();try {while (currentThreadName != 'C') {try {/* * 如果当前线程名字不是C，那么ThreadC就处理等待状态 */conditionC.await();} catch (InterruptedException e) {logger.severe(e.getLocalizedMessage());}}/* * 打印信息C */System.out.println("C");System.out.println();/* * 将当前线程值置为A 并通过ThreadA来执行 */currentThreadName = 'A';conditionA.signal();} finally {lock.unlock();}}}}}