After researching JEP: 312 Thread-Local-Handshakes and reading the excellent comments to this question, here is a quick summary. It is a performance enhancement which cannot be used directly by developers: A handshake mechanism is proposed as an optimisation of the Hotspot safepoints mechanism. The former allows threads in a safepoint to continue executing immediately after … Read more
Any diagram that shows a notify invocation bringing a thread from WAITING to RUNNABLE is wrong (or is using an unclarified shortcut). Once a thread gets awoken from a notify (or even from a spurious wakeup) it needs to relock the monitor of the object on which it was waiting. This is the BLOCKED state. … Read more
Whenever a thread calls the Thread.yield() method, it gives a hint to the thread scheduler that it is ready to pause its execution. The thread scheduler is free to ignore this hint. If any thread executes the yield method, the thread scheduler checks if there is any runnable (waiting to be executed) thread with same … Read more
It’s the same (and probably compiles to) as the x86 opcode PAUSE and equivalent the Win32 macro YieldProcessor, GCC’s __mm_pause() and the C# method Thread.SpinWait It’s a very weakened form of yielding: it tells your CPU that you are in a loop that may burn many CPU-cycles waiting for something to happen (busy-waiting). This way, … Read more
It’s fine to use Thread.sleep in that situation. The reason people discourage Thread.sleep is because it’s frequently used in an ill attempt to fix a race condition, used where notification based synchronization is a much better choice etc. In this case, AFAIK you don’t have an option but poll because the API doesn’t provide you … Read more
The JVM exits when all the running threads are daemon threads. So imagine you’re writing a simple game where your main method loops until you decide to quit. And imagine that at the start of the game, you start a thread that will endlessly poll some website to trigger alerts. You would like the JVM … Read more
Probably simplest and preferred solution is in Marco13’s answer so don’t get fooled by vote difference (this answer is few years older) or acceptance mark (it just means that this solution was appropriate for OP circumstances, not that it is best in general). You can use ThreadFactory to set threads inside Executor to daemons. This … Read more
To be able to call notify() you need to synchronize on the same object. synchronized (someObject) { someObject.wait(); } /* different thread / object */ synchronized (someObject) { someObject.notify(); }
A wait can be “woken up” by another thread calling notify on the monitor which is being waited on whereas a sleep cannot. Also a wait (and notify) must happen in a block synchronized on the monitor object whereas sleep does not: Object mon = …; synchronized (mon) { mon.wait(); } At this point the … Read more
Probably you already read the documentation description about them, I won’t repeat them, instead I will try to give answer with my own words, hope they will help you. Service is like an Activity but has no user interface. Probably if you want to fetch the weather for example you won’t create a blank activity … Read more