Rounding Decimals in Java

Question

So, I was making a program, where I have the user insert a numerator and denominator, the program converts the pseudo-fraction, to a decimal. It works fine, just one thing. One, if I enter a fraction that is a repeating decimal, (ex. 1/3, 0.3333333...), I want either it say 0.33 repeat, or for irrational numbers, It would round it after let's say 7 digits, and then stop and have "... Irrational" after. How could I do this? Code is below.

package Conversions;

import java.util.*;

public class FractionToDecimal  {

public static void main (String[] args) {
    Scanner sc = new Scanner (System.in);

    System.out.println("Enter Numerator: ");
    int numerator = sc.nextInt();
    System.out.println("Enter Denominator: ");
    int denominator = sc.nextInt();
    if (denominator == 0) {
        System.out.println("Can't divide by zero");
    }
    else {
        double fraction = (double)numerator / denominator;
        System.out.println(fraction);
    }
}
}

SO is not the place to go for having someone to write your code for you. You need to do your own homework. Keep working at it and when you have a more specific question, feel free to ask. — Kelly Keller-Heikkila, Nov 03 '15 at 01:05
duplicate of http://stackoverflow.com/questions/153724/how-to-round-a-number-to-n-decimal-places-in-java — Andrey Mormysh, Nov 03 '15 at 01:22

LBes · Accepted Answer · 2015-11-03T01:11:55.073

You could use this:

DecimalFormat df = new DecimalFormat("#.######");
df.setRoundingMode(RoundingMode.CEILING);

Add as many # as you want decimals and then ou can simply use it like this:

Double d = 12345.789123456;
System.out.println(df.format(d));

Using three # would give you for the example above: 12345.789 for instance.

Please note that you can pick your rounding mode of course.

Small other note: Next time you ask a question on SO, please show some research, there are thousands of post about this and thousands of tutorials online. It would be nice to show what you have tried, what doesn't work ...

Rounding Decimals in Java

1 Answers1