学习练习 java 验证码练习时间:2023-03-08 23:04:47 String str="1234567890qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM "; int b[]=new int[4]; Random a =new Random(); for(int i=0;i<4;i++) { b[i]=a.nextInt(62); System.out.print(str.substring((b[i]),(b[i]+1) )+" "); }