1. 使用ReentrantLock

import java.util.concurrent.locks.ReentrantLock;public class TestReentrantLock {  public static void main(String[] args) {    final ReentrantLock reentrantLock = new ReentrantLock(true);        reentrantLock.lock();    new Thread("Thread 1") {      public void run() {        for (int i = 1; i < 5; i++) {          reentrantLock.lock();          System.out.println(Thread.currentThread().getName() + " print " + i);          reentrantLock.unlock();        }      }    }.start();    new Thread("Thread 2") {      public void run() {        for (int i = 1; i < 5; i++) {          reentrantLock.lock();          System.out.println(Thread.currentThread().getName() + " print " + i);          reentrantLock.unlock();        }      }    }.start();    System.out.println(Thread.currentThread().getName() + " Done");    reentrantLock.unlock();  }}

结果为：

main DoneThread 1 print 1Thread 1 print 2Thread 1 print 3Thread 1 print 4Thread 2 print 1Thread 2 print 2Thread 2 print 3Thread 2 print 4