INTRODUCTION TO OBJECTS AND INPUT/OUTPUT - Java Programming: From Problem Analysis to Program Design - page 143

EXAMPLE 3-11

Consider the following statements:

String str;
int num1 = 45;
int num2 = 56;
int sum;

3

str = "The two numbers are: " + num1 + " and " + num2 + "\n";
sum = num1 + num2;

str = str + "The sum of the numbers is: " + sum + "\n";

str = str + "That is all for now!";
Figure 3-11 shows the output of the statement:

JOptionPane.showMessageDialog( null , str, "Summing Numbers",
JOptionPane.ERROR_MESSAGE);

FIGURE 3-11 Message dialog box showing the output of the string str

The class JOptionPane is contained in the package javax.swing . Therefore, to use this
class in a program, the program must import it from the package javax.swing .The
following statements illustrate how to import the class JOptionPane (you can use either
format):

import javax.swing.JOptionPane;

or:

import javax.swing.*;
System.exit

In order to use the input/output dialog boxes and properly terminate program execution,
the program must include the following statement:

System.exit(0);