Java:哈希图中的复合键 [英] Java: Composite key in hashmaps

问题描述

我想将一组对象存储在hashmap中，其中键应是两个字符串值的组合.有没有办法做到这一点?

I would like to store a group of objects in a hashmap , where the key shall be a composite of two string values. is there a way to achieve this?

我可以简单地将两个字符串连接起来，但是我确定有更好的方法来实现这一点.

i can simply concatenate the two strings , but im sure there is a better way to do this.

推荐答案

您可以有一个包含两个字符串的自定义对象:

You could have a custom object containing the two strings:

class StringKey {
    private String str1;
    private String str2;
}

问题是，您需要确定两个此类对象的相等性测试和哈希码.

Problem is, you need to determine the equality test and the hash code for two such objects.

相等性可以是两个字符串的匹配项，并且哈希码可以是串联成员的哈希码(这值得商)):

Equality could be the match on both strings and the hashcode could be the hashcode of the concatenated members (this is debatable):

class StringKey {
    private String str1;
    private String str2;

    @Override
    public boolean equals(Object obj) {
        if(obj != null && obj instanceof StringKey) {
            StringKey s = (StringKey)obj;
            return str1.equals(s.str1) && str2.equals(s.str2);
        }
        return false;
    }

    @Override
    public int hashCode() {
        return (str1 + str2).hashCode();
    }
}

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