import java.util.Random;import java.util.Scanner;publicclassTest{publicstaticvoidmain(String[] args){while(true){
String n =getCaptcha();
System.out.println("验证码为:"+n);
System.out.println("请输入验证码:");
Scanner sc =newScanner(System.in);
String s = sc.next();if(s.equalsIgnoreCase(n)){
System.out.println("验证成功!!");break;}else{
System.out.println("验证码刷新,请重新输入!");}}}publicstatic String getCaptcha(){
StringBuilder sb =newStringBuilder();for(char i ='a'; i <='z'; i++){
sb.append(i);}for(char i ='A'; i <='Z'; i++){
sb.append(i);}for(char i ='0'; i <='9'; i++){
sb.append(i);}
StringBuilder s =newStringBuilder();
Random r =newRandom();for(int i =0; i <4; i++){int n = r.nextInt(62);
s.append(sb.charAt(n));}return s.toString();}}