![]() We’ll first notice the example and then comment on it. Let’s now see another way of calculating elapsed time. The Also Quick, Also Easy and More Likely to Be Correct Way: System.nanoTime() So, in short, you should avoid using the currentTimeMillis() method for calculating elapsed time if you need high precision. The results you get from the difference may be inaccurate because the method measures what we call “wall-clock time.” That means it can change for a variety of reasons, including changes in the system clock or even leap-seconds. The method returns a long value, which refers to the number of milliseconds since January 1st, 1970, in UTC. In the example above, we’re using the “System.currentTimeMillis()” static method. Simple delay function in java how to#First, we’ll show a quick example of how to perform the calculation, and after that we’ll explain the code: long start = System.currentTimeMillis() We start our list of ways to measure elapsed time in Java with a solution that’s easy but often incorrect. The Quick, Easy, and Often Incorrect Way: System.currentTimeMillis() Without further ado, let’s now cover some of the main ways to perform a calculation of elapsed time in Java. Calculating Elapsed Time in Java in All Shapes and Sizes We’ll cover that in more detail in the sections to come. Why is this distinction important? For now, understand that it’s going to be crucial to decide which one of several options is the right one to calculate elapsed time. The classic example here would be benchmarking a function for performance measurement purposes. This means calculating elapsed time for some reason that’s not related to the domain of your application, but rather, refers to some concern about the development itself. The second category is what I like to call “meta” motivation. A good example would be recording the time a worker clocks in and out and then calculating the amount of time worked. This is when you have to calculate the elapsed time of some event that is relevant to your application’s core business or domain. The first category is what I call the “business logic” motivation. ![]() When it comes to the motivations behind calculating elapsed time, we can broadly categorize them into two main groups. One of them refers to the type of elapsed time calculation. In order to make the right call for your scenario, there are several factors you must consider. There are several different ways of calculating elapsed time in Java. Java Elapsed Time Calculation: Not a Single Thing By the end of the post, you’ll be aware of the main ways in which you can perform this calculation, and you’ll be able to make an informed decision about the best alternative for your scenario. Then we’ll quickly turn our focus to the alternatives themselves, explaining the strengths and weaknesses of each one. We’ll start by covering the different types of elapsed time calculation one might need to perform. In this post, we’ll offer some guidance so you can decide the most appropriate option to use when calculating elapsed time in Java. Additionally, third-party libraries add their own options to the mix. You have different alternatives brought to you by the Java API itself-and don’t forget that Java 8 brought us an entirely new date and time API, based on the popular Joda-time open-source project. Then, we have the problem that, in Java, there are many ways of performing this calculation. Failing to take DST into account when you should, can and often does result in incorrect calculations. For a quick example, remember that many places around the world observe Daylight Savings Time. How hard could that be? As it turns out, it can be tricky.įor starters, we have the fact that time itself is a tricky concept. Calculating elapsed time in Java is one of those. Many things in programming sound like they should be easy, but are quite hard. ![]()
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