Java synchronized与Lock对象锁

package test;import java.util.concurrent.locks.Lock;import java.util.concurrent.locks.ReentrantLock;public class ThreadTest {private int j;private Lock lock=new ReentrantLock();public static void main(String [] args){ThreadTest tt=new ThreadTest();for(int i=0;i<2;i++){new Thread(tt.new Adder()).start();new Thread(tt.new Subtractor()).start();}}public class Subtractor implements Runnable {@Overridepublic void run() {while(true){synchronized (ThreadTest.this) {System.out.println("j--="+j--);}/*lock.lock();try {System.out.println("j--="+j--);} finally {lock.unlock();}*/}}}private class Adder implements Runnable{@Overridepublic void run() {while(true){synchronized (ThreadTest.this) {System.out.println("j++="+j++);}/*lock.lock();try {System.out.println("j++="+j++);} finally {lock.unlock();}*/}}}}