如何将一个对象添加到另一个对象集中 [英] How to add an object into another Object set
问题描述
我有两个班级.一个(Person) 用于getter 和setter,另一个(People) 用于计算数据.我的情况是,我使用 ResultSet
从数据库中获取数据,然后创建了一个 person 对象来存储行数据.然后我创建了 people 对象来存储所有的人.
I have two classes. One(Person) for getters and setters, and another(People) for compute the data. What is my situation is, I get the data from the DB using ResultSet
, then created a person Object to store the row data. Then i created people Object to store all persons.
每个对象都创建为 SET.
Each Object created as SET.
while(rs.next())
{
Set<People> people = new HashSet<people>();
Person person = new Person();
String name = rs.getString(2);
person.setName(name);
int id = rs.getInt(1);
person.setId(id);
String dept = rs.getString(4);
person.setDept(dept);
int age = rs.getInt(3);
person.setAge(age);
people.add(person);
}
return people;
现在问题是While循环的最后一行people.add(person);
Now the problem is the last line in the While Loop people.add(person);
它说
类型Set中的add(People)方法不适用于参数(Person)
The method add(People) in the type Set is not applicable for the arguments (Person)
我该如何克服这个问题?
How can i overcome this problem?
谢谢.
推荐答案
我从你的设计中了解到你有一个 People has-many Person 关系,所以 People
类包含 Person
对象的集合.然后我会期待这样的事情:
My understandig from your design is that you have a People has-many Person relation, so the People
class holds a collection of Person
objects. Then I'd expect something like this:
public class Person {
private String name;
private Date dateOfBirth;
// .. more attributes
// getters and setters
// overrides of equals, hashcode and toString
}
public class People implements Set<Person> {
private Set<Person> persons = new HashSet<Person>();
public boolean add(Person person) {
return persons.add(person);
}
// more methods for remove, contains, ...
}
因此,在您的数据库相关代码中,您不需要创建另一个集合,因为 People
已经有了您需要的:
So in your database related code you wouldn't need to create another set, because People
already has the one you need:
People people = new People(); // or get it, if it's already created
while(rs.next())
{
Person person = new Person();
String name = rs.getString(2);
person.setName(name);
int id = rs.getInt(1);
person.setId(id);
String dept = rs.getString(4);
person.setDept(dept);
int age = rs.getInt(3);
person.setAge(age);
people.add(person);
}
return people;
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