java synchronized鎖對象，當對象引用是null的時候，鎖的是什么？謝邀！Java語言規(guī)范中明確指出如果鎖住的對象是null，則會NullPointerException，規(guī)范內(nèi)容如下：

java synchronized鎖對象，當對象引用是null的時候，鎖的是什么？

謝邀！

Java語言規(guī)范中明確指出如果鎖住的對象是null，則會NullPointerException，規(guī)范內(nèi)容如下：

The type of Expression must be a reference type， or a compile-time error occurs. A synchronized statement is executed by first evaluating the Expression. Then: If evaluation of the Expression completes abruptly for some reason， then the synchronized statement completes abruptly for the same reason. Otherwise， if the value of the Expression is null， a NullPointerException is thrown.