How can you round doubles to the nth decimal?

Question:

How can you round doubles to the nth decimal?

Answer:

Using the Math.round method and formating with the DecimalFormat class.

Code:

import java.text.DecimalFormat;
 
public class RoundDoubles {
   public static void main(String[] args) {
 
      double d1 = 0;
      double d2 = 1.49999;
      double d3 = 3.14159265359;
      double d4 = 98.5555555;
 
      //the number of zeros indicate the number of decimals.
      d1 = (double)Math.round(d1 * 100) / 100;
      d2 = (double)Math.round(d2 * 100) / 100;
      d3 = (double)Math.round(d3 * 100) / 100;
      d4 = (double)Math.round(d4 * 100) / 100;
 
      //the number of .0's indicate right padding.
      DecimalFormat df = new DecimalFormat("0.00"); 
      System.out.println(df.format(d1));
      System.out.println(df.format(d2));
      System.out.println(df.format(d3));
      System.out.println(df.format(d4));
   }
}

Output:

$ java RoundDoubles
0.00
1.50
3.14
98.56