/**
    *獲取指定位數密碼
    */
    public String getCode(int length){
        char[] m = new char[length];
        for(int i = 0;i < length;i++){
            m[i] = get();
        }
        return new String(m);
    }

    private char get(){
        int begin = 0;
        int end = 0;
        switch(new
 
 Random().nextInt(3)){
        case 0:
            begin = 10;
            end = 48;
            break;
        case 1:
            begin = 26;
            end = 65;
            break;
        case 2:
            begin = 26;
            end = 97;
            break;
        }
        return (char) (new
 
 Random().nextInt(begin) + end);
    }