Semaphore

Question

synchornized getResource(){
semaphore -- ;
if( semaphore < 0 ){
wait(); //thread sleep and procedure pause here
do retrieve resource steps here
synchronized putResource(){
do put resource steps here
semaphore ++;
if( semaphore <= 0){
notify();
semaphore implementation is listed above,
and in order to use wait(), notify(), we should use
synchronized method or "synchronized(this)" code block
There is a question that I still don't understand:
If a synchronized method acquires the lock associated
with the object, whether or not the call of "putResource()" function would wait when the call of "getResource()" acquires the lock assoicated with the object?
if so, then why not deadlock occurs when a thread is sleeping in the sychronized method "getResource()" while another thread is trying to call "putResource()"
if not, then what is the meaning of "lock associated with object"? What I've learned about "lock associated with object" before is when someone acquires the lock of an object, others who want to access the object should wait for the lock in advance...

Answer 1

When a thread that has an object's monitor calls wait on that object, it releases the monitor as it goes into the wait state, so it is available for another thread to pick up and call notify.
Note that calling notify does not release the monitor, so the waiting (woken up) thread cannot execute until the notifying thread releases the monitor normally.
Ref: JLS 17.13, 17.14
http://java.sun.com/docs/books/jls/second_edition/html/memory.doc.html#28460