The main differences between wait() and sleep() are in their purpose, behavior, and usage:

  • wait():
    • Used in synchronized blocks or methods to release the lock and put the current thread into the waiting state.
    • It requires the thread to hold a lock (or monitor) before calling.
    • The thread remains in the waiting state until notified (via notify() or notifyAll()).
    • Can throw InterruptedException.
  • sleep():
    • Used to pause the execution of the current thread for a specified amount of time.
    • Does not release the lock, so other threads may not proceed while the current thread is sleeping.
    • Does not require synchronization and can be called from any context.
    • Can throw InterruptedException.

In summary, wait() is used for inter-thread communication within synchronized blocks, while sleep() is for pausing the thread for a specified duration without releasing the lock.