package lock.reentrantlock;import java.util.Random; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock;/*** 描述： 演示公平和不公平兩種情況*/ public class FairLock {public static void main(String[] args) {PrintQueue printQueue = new PrintQueue();Thread thread[] = new Thread[10];for (int i = 0; i < 10; i++) {thread[i] = new Thread(new Job(printQueue));}for (int i = 0; i < 10; i++) {thread[i].start();try {Thread.sleep(100);} catch (InterruptedException e) {e.printStackTrace();}}} }class Job implements Runnable {PrintQueue printQueue;public Job(PrintQueue printQueue) {this.printQueue = printQueue;}@Overridepublic void run() {System.out.println(Thread.currentThread().getName() + "開始打印");printQueue.printJob(new Object());System.out.println(Thread.currentThread().getName() + "打印完畢");} }class PrintQueue {private Lock queueLock = new ReentrantLock(true);public void printJob(Object document) {queueLock.lock();try {int duration = new Random().nextInt(10) + 1;System.out.println(Thread.currentThread().getName() + "正在打印，需要" + duration);Thread.sleep(duration * 1000);} catch (InterruptedException e) {e.printStackTrace();} finally {queueLock.unlock();}queueLock.lock();try {int duration = new Random().nextInt(10) + 1;System.out.println(Thread.currentThread().getName() + "正在打印，需要" + duration+"秒");Thread.sleep(duration * 1000);} catch (InterruptedException e) {e.printStackTrace();} finally {queueLock.unlock();}} }

針對tryLock()方法，它是很猛的，它不遵守設定的公平的規則
例如，當有線程執行tryLock()的時候，一旦有線程釋放了鎖，那么這個正在tryLock()的線程就能獲取到鎖，即使在它之前已經有其他線程正在等待隊列里等待了

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