When working with numbers in Java, it is often necessary to round a number to a certain number of decimal places.

This can be useful when dealing with financial calculations or when presenting data to users.

In this tutorial, we will show you how to write a Java program to round a number to n decimal places.

The Java programming language provides a built-in method for rounding numbers, called `Math.round()`

. This method rounds a floating-point number to the nearest integer.

However, we can use this method in combination with some mathematical operations to round a number to a specific number of decimal places.

To round a number to n decimal places in Java, we can use the following formula:

roundedNumber = Math.round(number * 10^n) / 10^n

In this formula, `number`

is the original number we want to round, and `n`

is the number of decimal places we want to round to.

We multiply the original number by `10^n`

, round the result to the nearest integer using `Math.round()`

, and then divide the result by `10^n`

to get the final rounded number.

Here’s a Java program that implements this formula:

import java.util.Scanner; public class RoundNumber { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); System.out.print("Enter a number: "); double number = scanner.nextDouble(); System.out.print("Enter the number of decimal places to round to: "); int decimalPlaces = scanner.nextInt(); double roundedNumber = Math.round(number * Math.pow(10, decimalPlaces)) / Math.pow(10, decimalPlaces); System.out.println("The rounded number is: " + roundedNumber); } }

In this program, we first ask the user to enter a number and the number of decimal places to round to using a `Scanner`

.

We then calculate the rounded number using the formula we discussed earlier and display it to the user.

To test this program, you can run it on your local machine and enter a number and the number of decimal places to round to when prompted.

The program will then output the rounded number.

In conclusion, rounding a number to a certain number of decimal places in Java is a simple process.

By using the `Math.round()`

method and some mathematical operations, we can round a number to n decimal places with ease.