introduce:
In Java multi-threaded programming, the wait() and sleep() methods are both tools used to control the suspension of thread execution. However, there are some important differences between them. This article will dive into the differences between the wait() and sleep() methods.
wait() method
1. The function of wait() method:
The wait() method puts the current thread into a waiting state until another thread wakes it up by calling the notify() or notifyAll() method on the same object.
2. How to use the wait() method:
- The wait() method must be called in a synchronized block, that is, inside a synchronized statement block or a synchronized method.
- After calling the wait() method, the current thread will release the lock and enter the waiting queue.
3. Features and precautions of the wait() method:
- Release lock: After executing the wait() method, the current thread will release the lock, allowing other threads to acquire the lock and execute it.
- Calling the wait() method outside the synchronized block will throw an IllegalMonitorStateException.
- Waiting threads can be woken up by the notify() or notifyAll() method.
- Need to pay attention to spurious wakeups (spurious wakeups), that is, threads may be woken up without being notified. Therefore, the wait condition needs to always be checked in the loop.
sleep() method
1. The function of the sleep() method:
The sleep() method causes the current thread to enter the pause state for a specified period of time without releasing the lock.
2. How to use the sleep() method:
- The sleep() method can be called anywhere.
- Control thread suspension by specifying time.
3. Features and precautions of the sleep() method:
- The lock will not be released: after executing the sleep() method, the current thread still holds the lock, and other threads cannot obtain the lock and execute it.
- An InterruptedException may be thrown, which can be caught and processed.
- Not affected by spurious wakeups: Since the sleep() method does not depend on notifications from other threads, there will be no spurious wakeups.
The difference between wait() method and sleep() method
The difference in function: The wait() method is used for communication and synchronization between threads, while the sleep() method is used to suspend the execution of the current thread.
The difference in usage: the wait() method must be called in a synchronized block, while the sleep() method can be called anywhere.
The difference in the handling of locks: The wait() method will release the lock, while the sleep() method will not release the lock.
The difference in the wake-up mechanism: The wait() method needs to wake up the waiting thread through the notify() or notifyAll() method, while the sleep() method automatically resumes execution after the specified time arrives.
The difference in false wake-up: Since the wait() method is affected by false wake-up, the waiting condition needs to be checked in the loop, while the sleep() method will not cause false wake-up.
Summarize:
The wait() method and the sleep() method are both methods of controlling a thread to suspend execution, but there are important differences between them. The wait() method is used for communication and synchronization between threads. When called in a synchronization block, the lock will be released, and the waiting thread needs to be awakened by the notify() or notifyAll() method. The sleep() method is used to suspend the execution of the current thread, and the lock will not be released when it is called anywhere, and the duration of the suspension is controlled by specifying the time. In actual development, choosing an appropriate method according to specific needs can better write efficient and correct multi-threaded programs.