ADDITIONAL JAVA TOPICS - Java Programming: From Problem Analysis to Program Design - page 970

You can use the Java class DecimalFormat to format decimal numbers in a specific
manner. The method format of the class DecimalFormat is applied to the decimal
value being formatted. The following steps explain how to use these features to format
decimal numbers:

1. Create a DecimalFormat object and initialize it to the specific format. Consider the
following statement:

DecimalFormat twoDecimal = new DecimalFormat("0.00");

This statement creates the DecimalFormat object twoDecimal and initializes it to
the string "0.00" . Each 0 in the string is a format flag. The string "0.00" specifies
the formatting of the decimal number. This string indicates that the decimal number
being formatted with the object twoDecimal will have at least one digit to the left
of the decimal point and exactly two digits to the right of the decimal point. If the
number being formatted does not meet the formatting requirement, that is, it does
not have digits at the specified places, those places are automatically filled with 0.
Moreover, suppose that you have the following statement:

DecimalFormat twoDigits = new DecimalFormat("0.##");

The object twoDigits can be used to format the number with two decimal places,
but the ## symbols indicate that trailing zeros will appear as spaces.
2. Next, use the method format of the class DecimalFormat . (Assume the first
declaration of Step 1.) For example, the statement:

twoDecimal.format(56.379);

formats the decimal number 56.379 as 56.38 (the decimal number is rounded).
The method format returns the string containing the digits of the formatted number.
3. The class DecimalFormat is included in the package java.text . You must
import this class into your program.

Example D-2 illustrates how to format the output of decimal numbers.

EXAMPLE D-2

//Program: Formatting output of decimal numbers using
//the class DecimalFormat

import java.text.DecimalFormat;

public class FormattingDecimalNum
{

public static void main(String[] args)
{

double x = 15.674; //Line 1

double y = 235.73; //Line 2

double z = 9525.9864; //Line 3