两个线程如何同时进入同步块？(How could the two threads enter the synchronized block at the same time?)

 发生了一些奇怪的事情。 当我进入synchronized块时，我尝试打印Thread的名称。在print语句之后，我进行了100000秒的husge暂停。 
 
@Override
public int getNextAvailableVm() {
    synchronized(this) {

        System.out.println(Thread.currentThread().getName());

        try {Thread.sleep(100000000);}catch(Exception exc){}

        String dataCenter = dcc.getDataCenterName();
        int totalVMs = Temp_Algo_Static_Var.vmCountMap.get(dataCenter);
        AlgoHelper ah = (AlgoHelper)Temp_Algo_Static_Var.map.get(dataCenter);
        .
        .
        .
   }
}
 
 但是当运行此方法时，将打印2个线程的名称。 
 
Thread-11
Thread-13
 
 在此之后，长时间停顿发生。 这是为什么 ？ 当第一个线程尚未离开块时，两个线程如何进入同步块？ 

There is some weird thing happening. As I enter the synchronized block,I try to print the name of the Thread.After the print statement,I make a husge pause of 100000 seconds. 
 
@Override
public int getNextAvailableVm() {
    synchronized(this) {

        System.out.println(Thread.currentThread().getName());

        try {Thread.sleep(100000000);}catch(Exception exc){}

        String dataCenter = dcc.getDataCenterName();
        int totalVMs = Temp_Algo_Static_Var.vmCountMap.get(dataCenter);
        AlgoHelper ah = (AlgoHelper)Temp_Algo_Static_Var.map.get(dataCenter);
        .
        .
        .
   }
}
 
But as this method is run,name oft the 2 threads are printed.
 
Thread-11
Thread-13
 
and it is after this that the long pause occurs. Why is that ? How could the two threads enter the synchronized block,when the first thread has yet not left the block ?

原文：https://stackoverflow.com/questions/18696565