练习——获取随机字符数组

练习——获取随机字符数组

需求

随机生成类似百度网盘提取码的四位密码，包含字母和数字。

示例代码

public static void main(String[] args) {
    char[] c = {'a','b','c','d','e','f','g','h','i','j'
            ,'k','l','m','n','o','p','q','r','s','t','u'
            ,'v','w','x','y','z','0','1','2','3','4','5'
            ,'6','7','8','9'};
    char[] m = new char[4];
    for (int i = 0; i < m.length; i++) {
        int r = (int)(Math.random() * c.length);
        m[i] = c[r];
    }
    for (int i = 0; i < m.length; i++) {
        System.out.print(m[i]);
    }
}Code language: JavaScript (javascript)

输出示例：

x7k2

逻辑拆解

封装为可复用的方法

public static char[] generateCode(int length) {
    char[] pool = {'a','b','c','d','e','f','g','h','i','j'
            ,'k','l','m','n','o','p','q','r','s','t','u'
            ,'v','w','x','y','z','0','1','2','3','4','5'
            ,'6','7','8','9'};
    char[] result = new char[length];
    for (int i = 0; i < length; i++) {
        int r = (int)(Math.random() * pool.length);
        result[i] = pool[r];
    }
    return result;
}

// 调用
public static void main(String[] args) {
    char[] code = generateCode(4);
    for (char ch : code) {
        System.out.print(ch);
    }
}Code language: JavaScript (javascript)

扩展：包含大写字母

char[] pool = {'a','b','c','d','e','f','g','h','i','j'
        ,'k','l','m','n','o','p','q','r','s','t','u'
        ,'v','w','x','y','z'
        ,'A','B','C','D','E','F','G','H','I','J'
        ,'K','L','M','N','O','P','Q','R','S','T'
        ,'U','V','W','X','Y','Z'
        ,'0','1','2','3','4','5','6','7','8','9'};Code language: JavaScript (javascript)

注意事项

提示：如需生成不重复字符的密码，需加入去重判断。