java加减乘除消息框显示结果

import javax.swing.JOptionPane; // import class JOptionPane

public class Operation {
// An addition program

public static void main( String args[] )
{
String firstNumber, // first string entered by user
secondNumber; // second string entered by user
int number1, // first number to add
number2, // second number to add
sum, // sum of number1 and number2
dif, // difference of number1 and number2
pro, //product of number1 and number2
cou; //cousuit of number1 and number2
// read in first number from user as a string
firstNumber =
JOptionPane.showInputDialog( "Enter first integer" );

// 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 the numbers
sum = number1 + number2;
dif = number1 - number2;
pro = number1 * number2;
cou = number1 / number2;
// display the results
JOptionPane.showMessageDialog(null,
"和为 " + sum +"\n"+
"差 为" + dif +"\n"+
"积为" + pro+"\n"+
"商为" + cou+"\n",
"Results",
JOptionPane.PLAIN_MESSAGE );

System.exit( 0 ); // terminate the program
}

}