1. Introduction

In this tutorial, we will create a Java program to round a number to n decimal places. Rounding is a fundamental operation when we wish to limit the number of decimal places, especially when dealing with monetary values or specific scientific calculations.

2. Program Steps

1. Define a class named RoundNumber.

2. Inside the class, define the main method.

3. Inside the main method, declare a double variable representing the number to be rounded.

4. Declare an int variable n representing the number of decimal places to which the number should be rounded.

5. Utilize Math.round() method along with Math.pow() to round the number to n decimal places.

6. Print the original number and the rounded number.

3. Code Program

public class RoundNumber { // Step 1: Define a class named RoundNumber

    public static void main(String[] args) { // Step 2: Define the main method

        // Step 3: Declare a double variable representing the number to be rounded
        double number = 123.456789;

        // Step 4: Declare an int variable n representing the number of decimal places
        int n = 3;

        // Step 5: Utilize Math.round() and Math.pow() to round the number to n decimal places
        double roundedNumber = Math.round(number * Math.pow(10, n)) / Math.pow(10, n);

        // Step 6: Print the original and rounded number
        System.out.println("Original Number: " + number);
        System.out.println("Rounded to " + n + " decimal places: " + roundedNumber);
    }
}

Output:

Original Number: 123.456789
Rounded to 3 decimal places: 123.457

4. Step By Step Explanation

– Step 1: A class named RoundNumber is defined.

– Step 2: The main method is defined within the RoundNumber class.

– Step 3: A double variable number is declared, representing the number to be rounded.

– Step 4: An int variable n is declared, representing the number of decimal places to which the number should be rounded.

– Step 5: The Math.round() method is used in combination with Math.pow() to achieve the rounding to n decimal places.

– Step 6: The original number and the roundedNumber are printed to the console.