Java Double Round off to 2 decimal always [duplicate]

Question

I am trying to round off the double values to 2 decimal digits, however it's not working in all scenarios

public static double round(double value, int places) {
    if (places < 0) throw new IllegalArgumentException();

    BigDecimal bd = new BigDecimal(value);
    bd = bd.setScale(places, RoundingMode.HALF_UP);
    return bd.doubleValue();
}

public static void main(String[] args) {
    System.out.println(round(25.0,2));  //25.0 - expected 25.00
    System.out.println(round(25.00d,2)); //25.0 - expected 25.00
    System.out.println(round(25,2));   //25.0 - expected 25.00
    System.out.println(round(25.666,2));  //25.67
}

In short, no matter whether decimal exists or not, always hold the values upto 2 decimal even if it needs to pad additional zeros.

Any help is appreciated!

Answer 1

There are two things that can be improved in your code.

First, casting double to BigDecimal in order to round it is very inefficient approach. You should use Math.round instead:

    double value = 1.125879D;
    double valueRounded = Math.round(value * 100D) / 100D;

Second, when you print or convert real number to string, you may consider using System.out.printf or String.format. In your case using format "%.2f" does the trick.

    System.out.printf("%.2f", valueRounded);

Answer 2

I use the format() function of String class. Much simpler code. The 2 in "%.2f" indicates the number of digits after the decimal point you want to display. The f in "%.2f" indicates that you are printing a floating point number. Here is the documentation on formatting a string (http://docs.oracle.com/javase/7/docs/api/java/util/Formatter.html#syntax)

double number = 12.34567;
System.out.println(String.format("%.2f", number));

Answer 3

This will work for you:

public static void main(String[] args) {

    DecimalFormat two = new DecimalFormat("0.00"); //Make new decimal format

    System.out.println(two.format(25.0)); 

    System.out.println(two.format(25.00d));

    System.out.println(two.format(25));

    System.out.println(two.format(25.666));

}

Answer 4

You are converting BigDecimal back to double which essentially trim the trailing zeros.

You can return either BigDecimal or BigDecimal.toPlainString().

public static String round(double value, int places) {
    if (places < 0) throw new IllegalArgumentException();

    BigDecimal bd = new BigDecimal(value);
    bd = bd.setScale(places, RoundingMode.HALF_UP);
    return bd.toPlainString();
}