Skip to main content

Putting a Java pogram to sleep

For a good night's sleep wear comfortable loose clothes, do not consume coffee or tea after 6:00 PM, and read something relaxing before going to bed. Old hat.

ok that's cool, but what if you want to put your Java Thread to sleep? Before Java SE 5, the most common way to put threads to sleep was by calling the sleep() method.


System.out.println("Sleeping for 150 ms");
Thread.sleep(150);
System.out.println("Sleeping for 2 seconds");
Thread.sleep(2 * 1000);
System.out.println("Sleeping for 50 nanoseconds");
Thread.sleep(0, 50);
Java2html

 

 

The sleep() method takes a long parameter that  represents the milliseconds we want the thread to sleep. If the time we want our thread to sleep can be easily represented in ms, then this method works out well, but if we want the thread to sleep for some seconds then we have to perform the conversion manually. Even worse, if we want the thread to sleep for nanoseconds, then we have to use the confusing sleep() method that takes 2 parameters as shown in the code above. Such code is not very readable.

Java SE 5 gives us better readability in the form of the TimeUnit class. TimeUnit is an enum that has defines constants for DAYS, HOURS, MICROSECONDS, MILLISECONDS, MINUTES, NANOSECONDS,  and SECONDS. TimeUnit also has a sleep() method which we can call on the appropriate constant to put the thread to sleep for the number of specified units.


System.out.println("Sleeping for 150 ms");
TimeUnit.MILLISECONDS.sleep(150);
System.out.println("Sleeping for 2 seconds");
TimeUnit.SECONDS.sleep(2);
System.out.println("Sleeping for 50 nanoseconds");
TimeUnit.NANOSECONDS.sleep(50);
Java2html

 

 

Besides this TimeUnit also provides methods for converting values among different time units. Using the TimeUnit enum is definetely preffered over using Thread.sleep() if you are using Java SE 5.

There is one line in the above code samples that I am not sure will work correctly. By "work correctly" I do not mean it will cause a compiler error, but it may not work as promised. Can anyone point out which line?

Discuss this post in the learning forum.



Note: This text was originally posted on my earlier blog at http://www.adaptivelearningonline.net
Labels:

Comments

Post a Comment

Popular posts from this blog

Inheritance vs. composition depending on how much is same and how much differs

I am reading the excellent Django book right now. In the 4th chapter on Django templates , there is an example of includes and inheritance in Django templates. Without going into details about Django templates, the include is very similar to composition where we can include the text of another template for evaluation. Inheritance in Django templates works in a way similar to object inheritance. Django templates can specify certain blocks which can be redefined in subtemplates. The subtemplates use the rest of the parent template as is. Now we have all learned that inheritance is used when we have a is-a relationship between classes, and composition is used when we have a contains-a relationship. This is absolutely right, but while reading about Django templates, I just realized another pattern in these relationships. This is really simple and perhaps many of you may have already have had this insight... We use inheritance when we want to allow reuse of the bulk of one object in other ...
3 comments
Read more

Commenting your code

Comments are an integral part of any program, even though they do not contribute to the logic. Appropriate comments add to the maintainability of a software. I have heard developers complain about not remembering the logic of some code they wrote a few months back. Can you imagine how difficult it can be to understand programs written by others, when we sometimes find it hard to understand our own code. It is a nightmare to maintain programs that are not appropriately commented. Java classes should contain comments at various levels. There are two types of comments; implementation comments and documentation comments. Implementation comments usually explain design desicisions, or a particularly intricate peice of code. If you find the need to make a lot of implementation comments, then it may signal overly complex code. Documentation comments usually describe the API of a program, they are meant for developers who are going to use your classes. All classes, methods and variables ...
Post a Comment
Read more

Running your own one person company

Recently there was a post on PuneTech on mom's re-entering the IT work force after a break. Two of the biggest concerns mentioned were : Coping with vast advances (changes) in the IT landscape Balancing work and family responsibilities Since I have been running a one person company for a good amount of time, I suggested that as an option. In this post I will discuss various aspects of running a one person company. Advantages: You have full control of your time. You can choose to spend as much or as little time as you would like. There is also a good chance that you will be able to decide when you want to spend that time. You get to work on something that you enjoy doing. Tremendous work satisfaction. You have the option of working from home. Disadvantages: It can take a little while for the work to get set, so you may not be able to see revenues for some time. It takes a huge amount of discipline to work without a boss, and without deadlines. You will not get the benefits (insuranc...
10 comments
Read more