There are two ways to measure elapsed execution time in Java either by using System.currentTimeinMillis()or by using System.nanoTime(). These two methods can be used to measure elapsed or execution time between two method calls or events in Java. Calculating elapsed time is one of the first things Java programmer do to find out how many seconds or millisecond a method is taking to execute or how much time a particular code block is taking. Most Java programmers are familiar with System.currentTimeInMillis()which is there from the beginning while a new version of more precise time measurement utility System.nanoTime is introduced in Java 1.5, along with several new features in a language like Generics, Enum types, autoboxing and variable arguments or varargs.