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monitorexit

leave synchronized region of code

Jasmin Syntax

     monitorexit 

Stack

Before	After
objectref	...
...

Description

This releases an exclusive lock that was previously obtained using monitorenter for the object objectref. If other threads are waiting for the object to become unlocked, one of the waiting threads will be able to acquire a lock on the object and proceed.

Note that a single thread can lock an object several times - the runtime system maintains a count of the number of times that the object was locked by the current thread, and only unlocks the object when the counter reaches zero (i.e. when the number of monitorenters and monitorexits applied to a given object are equal).

The monitorenter/monitorexit mechanism is used by the Java synchronized statement to coordinate access to an object among multiple threads.

Exceptioms

NullPointerException - objectref is null.

IllegalMonitorStateException - objectref was not previously locked by the current thread.

Bytecode

Type	Description
u1	monitorexit opcode = 0xC3 (195)

See Also

monitorenter

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Java Virtual Machine, by Jon Meyer and Troy Downing, O'Reilly Associates