Actually, I am a bit confused in regards of several explanation from website or blog about synchronization and thread-safe. I've done some research on different class of Core Java Api or Java Framework (Collections). And I've often noticed that some class are synchronize and thread-safe which means, at a time, only one thread can access the code.
But I need some precision:
A class is synchronize so its thread-safe ?
A class is not synchronized. Rather a method, or a block of code is synchronized.
Synchronization (using synchronized) is one way to make code thread-safe. There are other ways.
Or synchronize and thread-safe have two different meaning ?
Yes. They have different meanings.
And i've often noticed that some class are synchronize and thread-safe which means, at a time, only one thread can access the code.
Actually, if you "noticed" that, you were not paying attention!
With a synchronized method, only one thread can access the code while holding a given lock; i.e. you get mutual exclusion. If two threads use different locks, then you won't get mutual exclusion.
The other thing to note is that merely using synchronized does not guarantee thread-safety. You need to use it in the right way: