1.14 作业

String c = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        
        Random d = new Random();
        
        int d1 = d.nextInt(c.length()-1);
        
        int d2 = d.nextInt(c.length()-1);
        
        int d3 = d.nextInt(c.length()-1);
        
        int d4 = d.nextInt(c.length()-1);
        
        String c1 = c.substring(d1,(d1+1));
        
        String c2 = c.substring(d2,(d2+1));
        
        String c3 = c.substring(d3,(d3+1));
        
        String c4 = c.substring(d4,(d4+1));
        
        String c5 = c1+c2+c3+c4;//这是重点，前面那么啰嗦就为它铺垫的
        
        System.out.println("验证码："+c5);
        
        System.out.print("请输入上面的验证码：");
        
        Scanner sr = new Scanner(System.in);
        
        String d5 = sr.nextLine();
        
        if(d5.equalsIgnoreCase(c5))
        {
            System.out.print("正在跳转……");
        }
        else
        {
            System.out.println("请重新输入验证码");
        }