Floating-point numbers are decimal values, which can be rounded to n number of decimal places. There are 3 different ways to Round a Number to n Decimal Places in Java as follows:
- Using format Method
- Using DecimalFormat Class
- Multiply and Divide the number by 10n (n decimal places)
Example:
Input: number = 1.41421356237, round = 3 Output:1.414
Input: number = 0.70710678118, round = 2 Output:0.71
Method 1: Using format Method
The decimal number can be rounded by the inbuilt format() method supported by Java.
Syntax:
System.out.format("%.df", number);
Parameters: The first parameter accepts d digits to round off the number, the second argument accepts a number that is to be rounded.
Example:
Java
// Java Program to Round a Number to n Decimal Places// using format() Method// Importing required classesimport java.io.*;// Main classclass GFG { // Main driver method public static void main(String[] args) { // Declaring and initializing a double number double number = 3.141341435; // Rounding number to 2 decimal places // using format method System.out.format("%.2f", number); }} |
3.14
Method 2: Using DecimalFormat Class
DecimalFormat is a child class of the NumberFormat which is used to perform formatting of decimal numbers in java. We create an object of this class and pass in as arguments the format specified in form of #, with the number of # after decimal point indicating the number of digits we wish to output. By default, the number is rounded off to the ceiling value itself. The object of the DecimalFormat class invokes a method format() which takes as argument the number to be formatted.
Example 1:
Java
// Java Program to Round a Number to n Decimal Places// Using DecimalFormat Class// Importing required classesimport java.text.DecimalFormat;// Main classpublic class GFG { // Main driver method public static void main(String[] args) { // Declaring and initializing a double number double number = 145.34567; // Creating an object of DecimalFormat class DecimalFormat df_obj = new DecimalFormat("#.###"); // format() method is used to // print the desired number System.out.println(df_obj.format(number)); }} |
145.346
Note: In case we wish to round off the number to the floor, we invoke the Java in-built class RoundingMode. It has the following values for attributes as follows:
- FLOOR – for next nearest floor value
- CEILING – for next nearest ceiling value
Also do remember, this method can be invoked on the DecimalFormat class supported in-built method setRoundingMode(), which takes as an argument either RoundingMode.FLOOR or CEILING, and accordingly gives us the result.
Example 2:
Java
// Java Program to Round a Number to N Decimal Places// Using DecimalFormat Class// Importing required classesimport java.math.RoundingMode;import java.text.DecimalFormat;// Main classpublic class GFG { // Main driver method public static void main(String[] args) { // Declaring and initializing double double number = 9.97869896; // Creating an object of DecimalFormat class DecimalFormat df_obj = new DecimalFormat("#.####"); // Rounding number to the next lowest value // using setRoundingMode() df_obj.setRoundingMode(RoundingMode.FLOOR); // Printing the number in desired format // using format() method System.out.println(df_obj.format(number)); }} |
9.9786
Method 3: Multiply and Divide the number with 10n (n decimal places)
In this approach, we first Multiply the number by 10n using the pow() function of the Math class. Then the number is rounded to the nearest integer. At last, we divide the number by 10n. By doing this, we get the decimal number up to n decimal places.
Syntax:
number = Math.round(number*Math.pow(10,n))/Math.pow(10,n);
Example:
Java
// Java Program to Round a Number to n Decimal Places// Via Multiply and Divide the number with 10^n// Importing required classesimport java.io.*;// Main classclass GFG { // Main driver method public static void main(String[] args) { // Declaring and initializing double number double number = 12.983665; // Getting the number of decimal places required int n = 3; // Rounding off the number // using pow() and round() method of Math class number = Math.round(number * Math.pow(10, n)) / Math.pow(10, n); // Printing the rounded number System.out.println(number); }} |
Output
12.984
