首页 > 代码库 > Summary of HashMap in Java
Summary of HashMap in Java
The tricky thing is how to decide the key for a hashmap. Especially when you intend to use self-defined objects as key.
The simple rule is you have to overwrite hashcode() and equals() method.
Rule 1: x.equals(y) return true if x indeed is equal to y by your own logic;
Rule 2: if x.equals(y) then x.hashcode() == y.hashcode().
Ideally any two different objects have distinct hashcodes. But that‘t not possible since hashcode is used to generate real array index. Collisison has to happen. Thus in practice it‘s possible for two different objects to have same hashcode. Then equals() is used to tell one from the other.
声明:以上内容来自用户投稿及互联网公开渠道收集整理发布,本网站不拥有所有权,未作人工编辑处理,也不承担相关法律责任,若内容有误或涉及侵权可进行投诉: 投诉/举报 工作人员会在5个工作日内联系你,一经查实,本站将立刻删除涉嫌侵权内容。