验证码Demo

/**

 * 生成大小写去重.用户输入不区分大小写.
 * @author Lyc

 */

import java.util.Random;

import java.util.Scanner;

public class Test05_1 {

public static void main(String[] args) {
System.out.println("请输入验证码:");
String str = random();
System.out.println(str);
Scanner scan = new Scanner(System.in);
String X = scan.nextLine();
if((X.toUpperCase()).equals(str.toUpperCase())) {
System.out.println("验证码正确!");
}else {
System.out.println("抱歉,输入有误!");
}

}
/*
* 验证码算法
*/
public static String random() {
StringBuilder str = new StringBuilder();
int E = 26;
int X;
Random random = new Random();
boolean[] b = new boolean[E]; 
for(int i=0;i<5;i++) {
int c = random.nextInt(2);
do {
if(c==1) {
X = random.nextInt(E);
}else {
X = random.nextInt(E);
}
}while(b[X]==true);
b[X] = true;
if (c==0) {
str.append((char)('A'+ X));
}else {
str.append((char)('a'+ X));
}
}
return str.toString();
}