INTRODUCTION TO OBJECTS AND INPUT/OUTPUT - Java Programming: From Problem Analysis to Program Design - page 146

Formatting the Output Using the String Method format
Earlier in this chapter, you learned how to format the output on the standard output
device using the stream method printf . However, the method printf cannot be used
with output dialog boxes. Formatting the output in an output dialog box, particularly
decimal numbers, can be done using the String method format or the class
DecimalFormat . Next, we describe how to use the String method format .
Appendix D describes the class DecimalFormat .
An expression to use the String method format is:

String.format(formatString, argumentList)
where the meaning of the parameters formatString and argumentList is the same as
in the method printf . The value of the expression is a formatted string. The following
example shows how the method format works.

EXAMPLE 3-13

Suppose we have the following declarations and initializations:

double x = 15.674;
double y = 235.73;
double z = 9525.9864;

int num = 83;

String str;

Expression Value
String.format("%.2f", x) "15.67"
String.format("%.3f", y) "235.730"
String.format("%.2f", z) "9525.99"
String.format("%7s", "Hello") " Hello"
String.format("%5d%7.2f", num, x) " 83 15.67"
String.format("The value of num = %5d", num) "The value of num ¼ 83"
str = String.format("%.2f", z) str ¼ "9525.99"

Because the value of the String method format is a string, the method format can also
be used as an argument to the methods print , println ,or printf . Example 3-14
illustrates this concept.

EXAMPLE 3-14

public class StringMethodformat
{

public static void main (String[] args)