[SOLVED] syncrhronized methods

[jon80]

"If count is an instance of SynchronizedCounter, then making these methods synchronized has two effects:

First, it is not possible for two invocations of synchronized methods on the same object to interleave. When one thread is executing a synchronized method for an object, all other threads that invoke synchronized methods for the same object block (suspend execution) until the first thread is done with the object.

Second, when a synchronized method exits, it automatically establishes a happens-before relationship with any subsequent invocation of a synchronized method for the same object. This guarantees that changes to the state of the object are visible to all threads.

Note that constructors cannot be synchronized — using the synchronized keyword with a constructor is a syntax error. Synchronizing constructors doesn't make sense, because only the thread that creates an object should have access to it while it is being constructed." (1).

1. What exactly is a "happens before" relationship?
2. Is it necessary to use a condition.signal() or condition.signalAll() the other methods to wake up awaiting threads, or are other synchronized methods waiting upon the synchronized method queued automatically? Is this question at all relevant to synchronized methods?

NOTES:
1. Synchronized Methods (The Java™ Tutorials > Essential Classes > Concurrency)
2. Core Java Volume I Pg. 747 (761) ISBN: 978-0-13-235476-9.

[OrangeDog]

if X and Y are in a happens-before relationship then "X happens before Y"

the "synchronized" keyword automatically deals with wait/notify cycles on the method or code block so you don't have to worry there, unless you need more complex or fine-grained control