Another graphics verification code (type of formula)

Inadvertently on the Internet to see this formula type of graphics verification code, feel good. I've written another practice.
The code is as follows:
/** */ /**
* Random generation of an addition or multiplication of arithmetic expressions,
* Draw a graphical verification code for it and return the result of the expression.
*/
Package Greenis

Import Java.awt.Color;
Import Java.awt.Font;
Import Java.awt.Graphics;
Import Java.awt.image.BufferedImage;
Import java.io.IOException;
Import Java.io.OutputStream;
Import Java.util.Random;

Import Javax.imageio.ImageIO;

/** */ /**
* @author Greenis
* @date 2007-10-8
* @version 1.0
*/
public class Arithmeticvalidatecode
... {
A collection of numbers.
Private int[] Number = ... {0,1,2,3,4,5,6,7,8,9};
The collection of operators.
Private char[] operator = ... {' + ', ' x '};
Picture width.
private int width = 50;
Picture height.
private int height = 20;
An arithmetic expression.
private String expression;
Calculated results.
private int result;

/** *//**
* Generate an arithmetic expression and its corresponding result.
*/
Public Arithmeticvalidatecode ()
... {
int NUM1 = this.number[(int) (Number.length * Math.random ())];
int num2 = this.number[(int) (Number.length * Math.random ())];
Char oper = this.operator[(int) (Operator.length * Math.random ())];
This.expression = integer.tostring (NUM1) + character.tostring (oper) + integer.tostring (num2) + "=";

Switch (OPER)
... {
Case ' + ': This.result = num1 + num2; Break
Case ' x ': This.result = num1 * NUM2; Break
Default:this.result =-1; Break
}
}

/** *//**
* Generates a graphical validation code that contains an arithmetic expression and returns the result of an expression.
*
* @param os
* @return Result
*/
Public String Getvalidatecode (outputstream OS)
... {
//