代码如下：

[code="java"]
public class SomeObj {
public void print(int i){
System.out.println(Thread.currentThread().getName()+DateHelper.getNow()+ " " + i);
try {
wait(1000);
} catch (InterruptedException e) {
e.printStackTrace();

}
}
}
public
class ThreadA extends Thread{
private SyncTest st;
public ThreadA(SyncTest syncTest){
this.st=syncTest;
}

public void run(){
st.methodA();
}
}
public class SyncTest {
private volatile int i;

public static void main(String[] args) throws Exception {
    new SyncTest().startUp();
}

public void startUp(){
    for (int a = 0; a < 10; a++) {
        new ThreadA(this).start();
    }
}

private  SomeObj obj = new SomeObj();

public void methodA() {
    synchronized (obj) {
       obj.print(i);

System.out.println(Thread.currentThread().getName()+DateHelper.getNow() + " god is a girl");
i++;

    }
}

}

[/code]

    synchronized (obj) {  运行结果显示，同步代码块并没有被锁住，而把这行代码的obj替换成this或者随便其他的instance对象，都能锁住代码块。求解？

因为wait(1000)会将当前对象obj的控制权（即锁）交出去1秒
可以用Thread.sleep(1000)