Java重写equals和hashCode与泛型 [英] Java Overriding equals and hashCode with Generics
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问题描述
private class Couple< V extends Comparable< V>> {
私人V v1;
私人V v2;
public Couple(V v1,V v2){
this.v1 = v1;
this.v2 = v2;
$ / code $ / pre
我使用HashMap,夫妻类型。例如,如果我想在HashMap中插入一个新元素,我做了以下操作:
HashMap< Couple< V> ;, Integer> ; map = new HashMap< Couple< V>,Integer>();
map.put(new Couple(V)(v1,v2),new Integer(10));
我应该如何在Couple类中使用泛型重写equals和hashCode方法?
解决方案 示例equals()实现 Couple
可能类似于: @Override
public boolean equals(Object obj){
if(!(obj instanceof Couple))
return假;
if(obj == this)
return true;
Couple couple =(Couple)obj;
return(this.v1!= null&& this.v1.equals(couple.v1)
&& this.v2!= null&& this.v2.equals( couple.v2));
}
和hashcode()示例:
@Override
public int hashCode(){
final int prime = 31;
int result = 1;
result = prime * result +((v1 == null)?0:v1.hashCode());
result = prime * result +((v2 == null)?0:v2.hashCode());
返回结果;
}
In a java class i have the following code:
private class Couple<V extends Comparable<V>>{
private V v1;
private V v2;
public Couple(V v1, V v2){
this.v1 = v1;
this.v2 = v2;
}
}
I use an HashMap and i want to use keys with the Couple type. For example if i want to insert a new element in the HashMap i do the following:
HashMap<Couple<V>, Integer> map = new HashMap<Couple<V>, Integer>();
map.put(new Couple<V>(v1, v2), new Integer(10));
How should i Override the equals and hashCode methods in the Couple class using Generics?
解决方案 Sample equals() implementation for Couple
could be like:
@Override
public boolean equals(Object obj) {
if (!(obj instanceof Couple))
return false;
if (obj == this)
return true;
Couple couple = (Couple) obj;
return (this.v1 != null && this.v1.equals(couple.v1)
&& this.v2 != null && this.v2.equals(couple.v2));
}
And hashcode() example:
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((v1 == null) ? 0 : v1.hashCode());
result = prime * result + ((v2 == null) ? 0 : v2.hashCode());
return result;
}
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