sleep() vs. wait()

sleep() vs. wait()

CALLING LOCATION

wait() must be called from synchronized method / block

sleep() can be called from anywhere 

TARGET

wait() is instance specific method called on object (exists in Object class)

sleep() is static method called on thread (exists in Thread class) 

LOCKING

wait() releases the acquired lock when thread is waiting

Thread.sleep() keeps the lock even if thread is waiting

WAKE UP CONDITION

After wait() , thread will wake up when notify() or notifyAll() is called

After sleep() , thread will wake up when at least the time expires or call interrupt()

USAGE

sleep() is used to pause a Thread execution

wait() is used for Inter-thread communication