— Scott McNealy, Sun Microsystems Chairman, President and ceo

public void go() {
doStuff();
synchronized(this) {
criticalStuff();
moreCriticalStuff();
}
}
synchronizing 
methods

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networking 
and
threads
you are here
4
515
A
1
Thread A runs for awhile
Attempt to enter the increment() method.
The method is synchronized, so 
get the key
for this object
Put the value of balance into variable i.
Balance is 0, so i is now 0.
Set the value of balance to the result of i + 1.
Now balance is 1.
Return the key 
(it completed the increment() method).
Re-enter the increment() method and 
get the key
.
Put the value of balance into variable i.
Balance is 1, so i is now 1.
[now thread A is sent back to runnable, but since it has not 
completed the synchronized method, Thread A keeps the key] 
B
2
Thread B is selected to run
Attempt to enter the increment() method. The method is 
synchronized, so we need to get the key.
The key is not available.
[now thread B is sent into a ‘object lock not available lounge]
A
3
Thread A runs again, picking up where it left off
(remember, it still has the key)
Set the value of balance to the result of i + 1.
Now balance is 2.
Return the key
.
[now thread A is sent back to runnable, but since it 
has completed the increment() method, the thread 
does NOT hold on to the key]
B
4
Thread B is selected to run
Attempt to enter the increment() method. The method is 
synchronized, so we need to get the key.
This time, the key IS available, get the key.
Put the value of balance into variable i.
[continues to run...]

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