在Java多執行緒中，可以使用synchronized關鍵字來實現執行緒之間同步互斥，但在JDK1.5中新增加了ReentrantLock類也能達到同步的效果，並且在擴充套件功能上也更加強大。

package unit3;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Demo6_Run {
	public static void main(String[] args) {
		MyService service = new MyService();
		MyThread a1 = new MyThread(service);
		MyThread a2 = new MyThread(service);
		MyThread a3 = new MyThread(service);
		MyThread a4 = new MyThread(service);
		MyThread a5 = new MyThread(service);
		/*System.out.println(a1.getName());
		System.out.println(a2.getName());
		System.out.println(a3.getName());
		System.out.println(a4.getName());
		System.out.println(a5.getName());*/
		a1.start();
		a2.start();
		a3.start();
		a4.start();
		a5.start();
	}
}

class MyThread extends Thread {
	private MyService service;
	public MyThread(MyService service) {
		super();
		this.service = service;
	}
	
	public void run() {
		service.testMethod();
	}
}

class MyService {
	private Lock lock = new ReentrantLock();
	public void testMethod() {
		lock.lock();
		for (int i = 0; i < 5; i++) {
			System.out.println("ThreadName=" + 
		 Thread.currentThread().getName() + 
		 (" " + (i + 1)));
		}
		lock.unlock();
	}
}
 

從執行結果來看，當前執行緒列印完畢之後將鎖進行釋放，其他執行緒才可以繼續列印。執行緒列印的資料是分組列印，應為當前執行緒已經持有鎖，但執行緒之間列印順序是隨機的。