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Rounding Numbers to One Decimal Place in Java

Rounding numbers in Java programming language is a common mission that developers encounter. Whether developing a banking application that requires financial transactions to be processed to the nth cent, or crafting a weather app that needs temperature accuracy, managing decimals becomes indispensable.

In this article, we will delve into the issue of rounding numbers to 1 decimal place, a solution in Java language, and a step-by-step explanation of the necessary code.

Solution to the problem: Using Math Round Function

Java provides the Math class, loaded with functions designed to carry out common math tasks. For rounding numbers, specifically to 1 decimal place, we will be leveraging the Math.round function. This approach is swift, uncomplicated, and reliable.

Here’s a simple code snippet that demonstrates this:

double input = 123.456;
double output = Math.round(input * 10.0) / 10.0;

Let’s break it down, and go for a detailed, step-by-step tour of the Java code used here.

Detailed Breakdown of the Code

Our initial step is declaring our double variable “input”, this is the number we plan to round the decimal of. Following that, we use the Math.round function.

  • The ‘input * 10.0’ within the brackets of Math.round is to move the decimal point one position to the right. This action is crucial as the Math.round function operates by rounding to the nearest whole number.
  • Next, the division operation ‘/ 10.0’ is there to reset the decimal back to its original position, giving us our rounded number.

This can be encapsulated as:

public class Main {
    public static void main(String[] args) {
        double input = 123.456;
        double output = Math.round(input * 10.0) / 10.0;

This code leads to the printing of 123.5 in the console, demonstrating the successful rounding to 1 decimal place.

Understanding the Java Math Library

The Java Math library is a potent tool for Java developers. Apart from Math.round, it provides diverse functions like abs, max, min, sqrt, log, sin, cos, tan, etc. These built-in math functions in Java are made to facilitate handling mathematical calculations within your programs.

All these functions and characteristics make Math a core part of Java programming knowledge. Understanding how to round a number to 1 decimal point is just one simple illustration of its utility. Dive deeper into the library, and you’ll find a wide array of other useful functions for your coding conundrums.


Rounding numbers to 1 decimal place in Java is a manageable task, thanks to the Math library provided by Java. As we have demonstrated, this function is a powerful tool to have in your Java programming arsenal. Whether you’re a novice starting with Java or an experienced developer, understanding how to use Math.round and, more broadly, the Math library, is invaluable. Keep coding and keep exploring!

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