问题描述

如何存储唯一对象以避免java Set中的重复?

How to Store unique objects to avoid the duplicates in java Set?

例如

考虑 Employee 对象(员工 ID、姓名、薪水......)

Consider Employee object which (Employee Id, name, salary....)

需要在Set中添加的对象的员工列表.我们需要对需要通过Employee Id"标识的重复元素的Set进行限制.

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.

最好的方法是什么?

推荐答案

如果你使用的是 java.util.Set 的实现，它不应该允许重复，只要你的 equals 和 hashCode 方法已正确实现.不知道为什么你有 hashmap 和 hashtable 作为你的问题的标签.也许您应该改写您的问题并添加给您带来问题的代码?

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?

考虑您的

如果你使用Set，你的Employee应该有以下方法:

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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