//验证码 前四位是字母 最后一位是数字
public class test1 {
    public static void main(String[] args){
        char [] chars=new char[52];
        for (int i = 0; i <chars.length ; i++) {
            if(i<=25){
                chars[i]=(char)(i+97);
            }
            else{
                chars[i]=(char)(i+65-26);
            }

        }
        Random r=new Random();

        String code="";
        for (int i = 0; i <4 ; i++) {
            int index=r.nextInt(chars.length);
            code+=chars[index];
        }
        code+=r.nextInt(10);
        System.out.println(code);
    }

}

技巧

选中 shift+f6 就可以直接修改所有的相同命名的词

抽奖

//抽奖，五个红包，顺序随机不重复，抽五次
public class test1 {
    public static void main(String[] args){
        int[] array={2,88,8888,99999,30};
        int[] newarray=new int[array.length];
        Random r=new Random();
        for (int i = 0; i <array.length; ) {
            int index=r.nextInt(array.length);
            boolean flag=exit(newarray,array[index]);
            int pri=array[index];
            while (!flag){
                newarray[i]=pri;
                i++;
                break;

            }

        }
        for (int i = 0; i <newarray.length ; i++) {
            System.out.println(newarray[i]);

        }

    }
    public static boolean exit(int[] newarr,int b){
        for (int i = 0; i <newarr.length ; i++) {
            if(newarr[i]==b){
                return true;
            }

        }
        return false;
    }


}

二维数组