我正在阅读 JVM 规范,试图弄清楚如何正确处理监视器。他们在相关部分给出的示例如下所示:
0 aload_1 // Push f
1 dup // Duplicate it on the stack
2 astore_2 // Store duplicate in local variable 2
3 monitorenter // Enter the monitor associated with f
4 aload_0 // Holding the monitor, pass this and...
5 invokevirtual #5 // ...call Example.doSomething()V
8 aload_2 // Push local variable 2 (f)
9 monitorexit // Exit the monitor associated with f
10 goto 18 // Complete the method normally
13 astore_3 // In case of any throw, end up here
14 aload_2 // Push local variable 2 (f)
15 monitorexit // Be sure to exit the monitor!
16 aload_3 // Push thrown value...
17 athrow // ...and rethrow value to the invoker
18 return // Return in the normal case
Exception table:
From To Target Type
4 10 13 any
13 16 13 any
我无法弄清楚为什么需要第二个异常表条目。如果抛出异常,monitorexit
我真的想再次尝试退出监视器吗?据我所知,可能抛出的异常是NullPointerException
and IllegalMonitorStateException
。