Java Program To Round The Number To N Decimal Places

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Program To Round The Number To N Decimal Places

In this article we will see how we can round a number to N decimal places.

Concept:

We can round decimal number to a certain accuracy or n number of decimal places. It is used when we want to make calculation easier & makes results easier to understand, it is applicable only when exact values are not too important.

For example:

A number is 231.434343545 and we didn’t want the exact value , in that case we can reduce the floating part to 2 or 3 decimal places, which will make the number simpler and further simple use.

After rounding that number to 2 decimal places,  the number will be à 231.43
After rounding that number to 3 decimal places,  the number will be à 231.434

Now we will see one by one approach

Java program to round the number to n decimal places by using formatting approach
Java program to round the number to n decimal places DecimalFormat class
Java program to round the number to n decimal places using BigDecimal class

Method 1 : Java program to round the number to n decimal places by using formatting approach

We can round the decimal number to n decimal places by using formatting approach.

Approach:

Enter a decimal number.
Print the decimal number by formatting approach (using %df).

Program:

import java.util.Scanner;
public class Main 
{  
    public static void main(String[] args)
    {  
         // CREATING OBJECT 
        Scanner sc = new Scanner(System.in);  
        // TAKING STRING FORM USER 
        System.out.println("Enter number: ");  
        double n= sc.nextDouble();   
        // rounding number to 2 decimal places
        System.out.println("number: " + n);
        System.out.format("\n after rounding : %.3f", n);
    }
}

Output:

Enter number: 231.32525325
number: 231.32525325
after rounding : 231.325

Method 2 : Java program to round the number to n decimal places DecimalFormat class

We can round the decimal number to n decimal places by using DecimalFormat class approach . This class is a child class of NumberFormat . In this we create an object of this class and pass the arguments as the format specified in form of ”#”, with the number of # after the decimal point , which indicate how many n places we want to store after the decimal point .

Approach:

Enter a decimal number .
Create a object of DecimalFormat by giving the ‘N‘ no of ‘#‘ after the “.” (Ex- #.####)
Print the decimal number by the method format ().

Program:

import java.util.Scanner;
import java.text.DecimalFormat;
public class Main 
{  
    public static void main(String[] args)
    {  
         // CREATING OBJECT 
        Scanner sc = new Scanner(System.in);  
        // TAKING STRING FORM USER 
        System.out.print("Enter number: ");  
        double n= sc.nextDouble();   
        //creating obj. of the DecimalFormat 
         DecimalFormat d = new DecimalFormat("#.####");
        System.out.print("number: " + n);
        System.out.print("\nafter rounding : " + d.format(n));
    }
}

Output:

Enter number: 231.32525325
number: 231.32525325
after rounding : 231.3252

Method 3 : Java program to round the number to n decimal places using BigDecimal class

We can round the decimal number to n decimal places by using BigDecimal class approach .

Approach:

Enter a decimal number .
Create a object of BigDecimal class.
Round up the number by using setcsale() method .
Print that value .

Program:

import java.math.RoundingMode;
import java.util.Scanner;
import java.math.BigDecimal; 
public class Main 
{  
    public static void main(String[] args)
    {  
       // CREATING OBJECT 
        Scanner sc = new Scanner(System.in);  
        // TAKING STRING FORM USER 
        System.out.print("Enter number: ");  
        double n= sc.nextDouble();   
        System.out.print("Enter how many places you want : ");  
        int a= sc.nextInt(); 
        //creating obj. of the bigdecimal 
        BigDecimal bd = new BigDecimal(Double.toString(n));
        // rounding the value to desire n places 
        bd = bd.setScale(a, RoundingMode.HALF_UP);
        System.out.print("number: " + n);
        System.out.print("\nafter rounding : " + bd);
    }     
}

Output:

Enter number: 123.123456
Enter how many places you want : 4
number: 123.123456
after rounding : 123.1235

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