Java 内存模型
The JMM defines a partial ordering called happens-before on all actions within the program.
The rules for happens-before are:
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Program order rule. Each action in a thread happens-before every action in that thread that comes later in the program order.
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Monitor lock rule. An unlock on a monitor lock happens-before every subsequent lock on that same monitor lock.[3]
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Volatile variable rule. A write to a volatile field happens-before every subsequent read of that same field.[4]
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Thread start rule. A call to Thread.start on a thread happens-before every action in the started thread.
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Thread termination rule. Any action in a thread happens-before any other thread detects that thread has terminated, either by successfully return from Thread.join or by Thread.isAlive returning false.
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Interruption rule. A thread calling interrupt on another thread happens-before the interrupted thread detects the interrupt (either by having InterruptedException tHRown, or invoking isInterrupted or interrupted)
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Finalizer rule. The end of a constructor for an object happens-before the start of the finalizer for that object.
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Transitivity. If A happens-before B, and B happens-before C, then A happens-before C.
注意
Locks and unlocks on explicit Lock objects have the same memory semantics as intrinsic locks.
Reads and writes of atomic variables have the same memory semantics as volatile variables.
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