Sleep(): This Method is used to pause the execution of current thread for a specified time in Milliseconds. Here, Thread does not lose its ownership of the monitor and resume’s it’s execution
Wait(): This method is defined in object class. It tells the calling thread (a.k.a Current Thread) to wait until another thread invoke’s the notify() or notifyAll() method for this object, The thread waits until it reobtains the ownership of the monitor and Resume’s Execution.
| Wait() | Sleep() |
|---|---|
| Wait() method belongs to Object class. | Sleep() method belongs to Thread class. |
| Wait() method releases lock during Synchronization. | Sleep() method does not release the lock on object during Synchronization. |
| Wait() should be called only from Synchronized context. | There is no need to call sleep() from Synchronized context. |
| Wait() is not a static method. | Sleep() is a static method. |
|
Wait() Has Three Overloaded Methods:
|
Sleep() Has Two Overloaded Methods:
|
| public final void wait(long timeout) | public static void sleep(long millis) throws Interrupted_Execption |
Example For Sleep Method:
synchronized(monitor)
{
Thread.sleep(1000); Here Lock Is Held By The Current Thread
//after 1000 milliseconds, current thread will wake up, or after we call that is interrupt() method
}
Example For wait Method:
synchronized(monitor)
{
monitor.wait() Here Lock Is Released By Current Thread
}
Similarity Between Both wait() and sleep() Method:
- Both Make The Current Thread go Into the Not Runnable State.
- Both are Native Methods.
The Below Code Snippet For Calling wait() and sleep() Method:
Java
synchronized(monitor){ while(condition == true) { monitor.wait() //releases monitor lock } Thread.sleep(100); //puts current thread on Sleep } |
Program:
Java
// Java program to demonstrate the difference// between wait and sleepclass GfG{ private static Object LOCK = new Object();public static void main(String[] args) throws InterruptedException { Thread.sleep(1000); System.out.println("Thread '" + Thread.currentThread().getName() + "' is woken after sleeping for 1 second"); synchronized (LOCK) { LOCK.wait(1000); System.out.println("Object '" + LOCK + "' is woken after" + " waiting for 1 second"); }}} |
Output
Thread 'main' is woken after sleeping for 1 second Object 'java.lang.Object@1d81eb93' is woken after waiting for 1 second