如何存储独特的对象以避免java Set中的重复? [英] How to Store unique objects to avoid the duplicates in java Set?
问题描述
如何存储唯一对象以避免Java Set中的重复项?
例如
考虑Employee对象(Employee Id,name,salary ....)
对象的雇员列表需要在Set中添加。
我们需要限制Set对于需要通过员工ID识别的重复元素。
最好的方法是什么?
如果您正在使用 java.util.Set
的实现,只要你的等于
和 hashCode
方法正确实现,就不应该允许重复。不知道为什么你有hashmap和hashtable作为标签在你的问题,虽然。也许你应该改写你的问题,并添加代码给你的问题?
编辑:考虑您的编辑:
如果您使用 Set
,您的员工应该有以下方法:
@Override
public int hashCode(){
final int prime = 31;
int result = 1;
result = prime * result +((id == null)?0:id.hashCode());
返回结果;
}
@Override
public boolean equals(Object obj){
如果(this == obj)
返回true;
if(obj == null)
return false;
if(getClass()!= obj.getClass())
return false;
Employee other =(Employee)obj;
if(id == null){
if(other.id!= null)
return false;
} else if(!id.equals(other.id))
return false;
返回true;
}
How to Store unique objects to avoid the duplicates in java Set?
For example
Consider Employee object which (Employee Id, name, salary....)
list of employee of objects need to add in the Set. We need to restrict the Set for the duplicate elements which need to identify by the "Employee Id.
What are the best way's to do?
If you are using an implementation of a java.util.Set
, it should not allow duplicates as long as your equals
and hashCode
methods are implemented properly. Not sure why you have hashmap and hashtable as tags on your question though. Maybe you should rephrase your question and add the code that gives you issues?
Edit: considering your edit:
If you use a Set
, your Employee should have the following methods:
@Override
public int hashCode() {
final int prime = 31;
int result = 1;
result = prime * result + ((id == null) ? 0 : id.hashCode());
return result;
}
@Override
public boolean equals(Object obj) {
if (this == obj)
return true;
if (obj == null)
return false;
if (getClass() != obj.getClass())
return false;
Employee other = (Employee) obj;
if (id == null) {
if (other.id != null)
return false;
} else if (!id.equals(other.id))
return false;
return true;
}
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