java how to get elapsedTime

To get the elapsed time in Java, you can use the System.nanoTime method or the Instant.now method of the java.time package.

Here is an example of how to get the elapsed time in Java using the System.nanoTime method:

long startTime = System.nanoTime();

// code to be measured goes here

long endTime = System.nanoTime();
long elapsedTime = endTime - startTime;
System.out.println(elapsedTime + " nanoseconds");

In this example, the System.nanoTime method is used to get the current time in nanoseconds since the epoch (the point in time at which the time is 0). The startTime variable is initialized with the current time before the code to be measured is executed. After the code has been executed, the endTime variable is initialized with the current time again. The elapsed time is then calculated by subtracting the startTime from the endTime and storing the result in the elapsedTime variable. The elapsedTime variable is then printed to the console using the println method of the System.out object.

This example will output a long integer value similar to the following to the console:

1234 nanoseconds

Which represents the elapsed time in nanoseconds.

You can also use the Instant.now method of the java.time package to get the elapsed time as a Duration object:

import java.time.Duration;
import java.time.Instant;

Instant startTime = Instant.now();

// code to be measured goes here

Instant endTime = Instant.now();
Duration elapsedTime = Duration.between(startTime, endTime);
System.out.println(elapsedTime + " seconds");

In this example, the Instant.now method is used to get the current time as an Instant object. The startTime variable is initialized with the current time before the code to be measured is executed. After the code has been executed, the endTime variable is initialized with the current time again. The elapsed time is then calculated by calling the Duration.between method and passing it the startTime and endTime variables. The resulting Duration object is stored in the elapsedTime variable and printed to the console using the println method of the System.out object.

This example will output a string similar to the following to the console:

PT0.001234S

Which represents the elapsed time in the ISO-8601 format.

You can use these methods to measure the elapsed time of a specific code block in your Java applications. You can then use the java.time package or other libraries to manipulate and format the elapsed time as needed.