Sleep vs Wait: Difference and Comparison

Java has several methods to carry out certain actions.

A method is a group of code which runs only when it is called; and may or may not return a result.

Methods like sleep and wait are used for multithreading. Both of them pause and sends the thread into waiting but have major differences in functioning.

Key Takeaways

  1. “Sleep” is a state of rest in which the body and mind are inactive, while “Wait” is staying in one place or delaying action until a specific event occurs.
  2. “Sleep” is a natural and necessary bodily function, while “Wait” is a voluntary action that can be chosen or avoided.
  3. “Sleep” is associated with nighttime, while “Wait” can occur at any time of the day.

Sleep vs Wait

The difference between the sleep() and wait() method is that the sleep() method is used in the program to pause the execution of the current thread for a particular time period while the wait() method is used in the program to pause or suspend the current thread until specific methods are invoked.

Sleep vs Wait

During the use of the sleep method, the current thread does not lose ownership of the monitor.

Sleep is a static method and is a part of the class thread. After the wait time gets over, the thread goes back to the original runnable state.

It ensures complete utilization of the CPU while waiting.

Whereas the wait() method is used in the Java program to order the current thread to wait until another thread is not invoked for that object.

The thread then continues with the execution once it obtains control of the monitor.

It is not a static method, unlike sleep, and is part of an object class.

Comparison Table

Parameters of comparisonSleepWait
ClassThe sleep method is a part of thread class The wait method is a part of object class
Type of methodSleep is a static methodWait is not a static method
Calling techniqueThe sleep method can be called from outside the synchronized contextThe wait method can be called only from the synchronized context
Lock releaseSleep method does not release the lock on the object, for the specified timeout, during synchronizationWait method releases the lock on the object, to have a chance to execute, during synchronization
Declarationpublic static void sleep() public final void wait()

What is Sleep?

The thread sleep() is a static method in Java program which suspends the current thread and puts it in a wait state for a stipulated time period.

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Once the wait state and time are over, the thread condition is changed to a runnable state. And then waits for the CPU for further execution.

The aim of this method is to create a delay for a few seconds in the program and simultaneously have maximum utilization of the CPU.

If the system is busy or overloaded, then the wait or pause time is more, and otherwise, it would be less or equal to the actual time.

The return type of sleep method can be said void, as it does not return any value.

Sleep thread does not lose the monitor or lock the thread that it has acquired already.

If, in any case, the sleep is disturbed, the thread would throw Interrupted_Exception.

The actual duration for which the thread would sleep depends on the schedulers and system timers which are a part of the operating system.

The syntax of the sleep method is – public static void sleep(long milliseconds)

public static void sleep(long milliseconds, int nanoseconds)

Here milliseconds and nanoseconds are the time for which the thread would sleep.


What is Wait?

Wait() is a method used for inter-thread communication.

Whenever the wait() thread is used, the calling or current thread is paused and suspended until methods like notify() or notifyAll() are invoked in the system.

notify() method would wake specified threads while notifyAll() is applicable for every thread.

When synchronized, the wait method gives up the lock to the resources.

There is no return value of the Wait method, hence it can be said that it returns void.

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The two exceptions of the Wait method are Interrupted_Exception (when the current thread is interrupted during its sleep) and IllegalMonitorStateException (when the current thread is not the owner of the object on the monitor).

The Wait method is a part of the object class. The method is only applicable and can be called over a synchronized block.

The wait method sets the suspended or locked screen free during synchronization.

And the Wait method exclusively allows the synchronized multiple threads to access the same object one by one.

The syntax of the Wait method is – public final void wait()


Main Differences Between Sleep and Wait

  1. The Sleep method causes the thread to sleep for a specified and particular time period, for specified timeout unless expired or interrupted, while the Wait method causes the thread to sleep until methods like notify() or notifyAll() are invoked.
  2. The Sleep method executes on a thread, while the Wait method executes on an object.
  3. The Sleep method is used for time synchronisation, while the Wait method is used for multiple-thread synchronization.
  4. During the Wait thread, synchronized multiple threads can access the same object adjacently, while in the Sleep thread, synchronized multiple threads have to wait for the sleep of the current thread to get over.
  5. The Wait method sets the lock or monitor free, while the Sleep method does not set the monitor free during sleep or wait of the current thread.
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Last Updated : 31 July, 2023

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18 thoughts on “Sleep vs Wait: Difference and Comparison”

  1. The article effectively elucidates the variances between the sleep and wait methods, providing a clear and concise comparison. The details of synchronization and lock release are particularly helpful.

    • The article does an excellent job of delineating the differences between the sleep and wait methods. The information about synchronization and lock release is presented with clarity and precision.

  2. The detailed explanation of the sleep and wait methods is excellent. This article is a valuable asset for anyone seeking to enhance their understanding of these fundamental Java concepts.

  3. This is a comprehensive comparison of the sleep and wait methods in Java. The article clearly outlines the key differences and provides a useful comparison table for reference.

    • The detailed breakdown of the sleep and wait methods is very insightful. It’s valuable to understand the nuances and functionalities of these methods in Java programming.

    • I found the explanation of the sleep and wait methods to be informative and precise. The comparison table is particularly helpful in summarizing the contrasting features of these methods.

  4. The article delivers a thorough comparison between the sleep and wait methods in Java. I appreciate the detailed explanations, which offer valuable insights into their functionalities.

    • I found the article to be informative and well-crafted. The explanations of sleep and wait methods are conducive to a better understanding of their usage and implications in Java.

  5. The article offers a detailed comparison of the sleep and wait methods, providing comprehensive insights into their behaviors and functionalities within Java programming.

  6. This article is a valuable resource for understanding the sleep and wait methods in Java. The explanations are detailed, and the comparison table offers a convenient reference for understanding the disparities between these methods.

    • I share the same sentiment, Vmorgan. The comparison table provides a clear overview of the differences, and the detailed descriptions enhance comprehension of the sleep and wait methods.

  7. Thank you for the article. I appreciate the detailed explanation of the differences between the sleep and wait methods. It’s good to have a clear understanding of how they function in the Java program.

    • Your explanation of the concept is very well-structured and easy to understand. I agree that it’s crucial to have clarity on these fundamental methods.

  8. The distinction between the sleep and wait methods was explained thoroughly in this article. I found the explanation of the wait method’s behavior during synchronization to be particularly illuminating.

    • I agree, Freya. The article provides a clear and precise explanation of the wait method’s behavior, making it easier to comprehend its functionality in Java.

    • The article’s description of the behaviors and return types of the sleep and wait methods is highly informative. Understanding these differences is essential for effective multithreading in Java.

  9. I found the article to be highly informative and insightful. The in-depth analysis of the sleep and wait methods greatly contributes to understanding their nuances and implications in Java.

  10. The article provides a comprehensive analysis of the sleep and wait methods in Java. The explanations are well-organized and greatly contribute to a deeper understanding of these fundamental methods.


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