java简单验证码生成程序

下面的函数，返回的字符串就是所需验证码

public String id(){

        Random ra =new Random();
        st="";
        String [] w= {"0","1","2","3","4","5","6","7","8","9","K","Q","p","m","n","b","w","z","x","g","t","y","f"};
        for(int i=0;i<4;i++)
        {
            st=st+w[ra.nextInt(23)];
        }
        return st;

    }

思路就是利用字符串数组设置所需验证码包含的字符种类，然后利用取随机数的方法取出要求个数的随机字符，把它们依次拼接在新的字符串中并返回，这样就实现了随机生成验证码的目的。