// Fig. 2.9: Addition.java
// Addition program that displays the sum of two numbers.

// Java packages
import javax.swing.JOptionPane;  // program uses JOptionPane

public class Addition {

  // main method begins execution of Java application
  public static void main( String args[] )
  {
    String firstNumber;   // first string entered by user
    String secondNumber;  // second string entered by user

    int number1;          // first number to add
    int number2;          // second number to add
    int sum;              // sum of number1 and number2

    // read in first number from user as a String
    do {
      firstNumber = JOptionPane.showInputDialog( "Enter first integer" );
    } while (firstNumber == null);

    // read in second number from user as a String
    secondNumber =
        JOptionPane.showInputDialog( "Enter second integer" );

    // convert numbers from type String to type int
    number1 = Integer.parseInt( firstNumber );
    number2 = Integer.parseInt( secondNumber );

    // add numbers
    sum = number1 + number2;

    // display result
    JOptionPane.showMessageDialog( null, "The sum is " + sum,
                                   "Results", JOptionPane.PLAIN_MESSAGE );

    System.exit( 0 );   // terminate application with window

  } // end method main

} // end class Addition