Java Set集合 - 覆盖equals方法 [英] Java Set collection - override equals method
问题描述
有没有办法覆盖 Set
数据类型使用的 equals
方法?我为一个名为 Fee
的类编写了一个自定义等于
的方法。现在我有一个 LnkedList
费用
,我想确保没有重复的条目。因此,我正在考虑使用 Set
设置 LinkedList
,但决定两项费用是否相等的标准存在于费用
类中的覆盖等于
方法。
Is there any way to override the the equals
method used by a Set
datatype? I wrote a custom equals
method for a class called Fee
. Now I have a LnkedList
of Fee
and I want to ensure that there are no duplicated entries. Thus I am considering using a Set
insted of a LinkedList
, but the criteria for deciding if two fees are equal resides in the overriden equals
method in the Fee
class.
如果使用 LinkedList
,我将不得不迭代每个列表项并在<$中调用overriden equals
方法c $ c>费用类,其余条目作为参数。仅仅阅读这个听起来就像处理太多会增加计算复杂性。
If using a LinkedList
, I will have to iterate over every list item and call the overriden equals
method in the Fee
class with the remaining entries as a parameter. Just reading this alone sounds like too much processing and will add to computational complexity.
我可以使用设置
重写等于
方法?我应该吗?
Can I use Set
with an overridden equals
method? Should I?
推荐答案
正如杰夫福斯特所说:
Set.equals()方法仅用于比较两个集合是否相等。
The Set.equals() method is only used to compare two sets for equality.
您可以使用设置
以删除重复的条目,但要注意: HashSet
不使用等于()
包含对象的方法以确定相等。
You can use a Set
to get rid of the duplicate entries, but beware: HashSet
doesn't use the equals()
methods of its containing objects to determine equality.
A HashSet
带有内部 HashMap
与<整数(HashCode),对象>
条目并使用equals()以及equals方法 HashCode 以确定相等。
A HashSet
carries an internal HashMap
with <Integer(HashCode), Object>
entries and uses equals() as well as the equals method of the HashCode to determine equality.
解决此问题的一种方法是覆盖 hashCode()
在您放入Set的类中,以便它代表您的 equals()
条件
One way to solve the issue is to override hashCode()
in the Class that you put in the Set, so that it represents your equals()
criteria
例如:
class Fee {
String name;
public boolean equals(Object o) {
return (o instanceof Fee) && ((Fee)o.getName()).equals(this.getName());
}
public int hashCode() {
return name.hashCode();
}
}
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