Question

我有一种递归生成随机密码的方法，需要至少有一个大写字母。我已经设置了方法，但由于某种原因它告诉我，当我已经在if语句中定义了return类型时，该方法必须返回String类型。

问题：如何让此错误消失或修复我的方法以使其返回密码？

public static char[]chars = {'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','!','@','$','%','^','&'};

            public static String generatePassword(Random rand, String password, int position, int size) //this method must return a result of type String
            {
                boolean isLowerCase = rand.nextBoolean();
                int randomChar = rand.nextInt(chars.length);
                char c = chars[randomChar];
                if(position == size) //base case
                {
                    return password; //string is returned here? 
                }
                if(isLowerCase)
                {
                    generatePassword(rand, password + c, position + 1, size);
                }
                else //its either upper or lower case
                {
                    generatePassword(rand, password + Character.toUpperCase(c), position + 1, size);
                }

Answer 1

在所有执行组合的方法中，应该返回一个String。这是你的方法应该是这样的。

    public static String generatePassword(Random rand, String password, int position, int size) //this method must return a result of type String
    {
        boolean isLowerCase = rand.nextBoolean();
        int randomChar = rand.nextInt(chars.length);
        char c = chars[randomChar];
        if(position == size) //base case
        {
            return password; //string is returned here? 
        }
        if(isLowerCase)
        {
            return generatePassword(rand, password + c, position + 1, size);
        }
        else //its either upper or lower case
        {
            return generatePassword(rand, password + Character.toUpperCase(c), position + 1, size);
        }
     }

Answer 2

对我来说这似乎是递归解决方案的一个不好的地方，我建议您使用StringBuilder和单static Random。以及方法的单个size参数。像，

private static Random rand = new Random();
public static String generatePassword(int size) {
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < size; i++) {
        int randomChar = rand.nextInt(chars.length);
        char ch = chars[randomChar];
        if (Character.isLetter(ch)) {
            if (rand.nextBoolean()) {
                ch = Character.toUpperCase(ch);
            }
        }
        sb.append(ch);
    }
    return sb.toString();
}

方法不允许返回字符串

2 个答案: