容器的小疑点

//Person类public class Person {    private String name;    private int age;    public Person() {        super();    }    public Person(String name, int age) {        super();        this.name = name;        this.age = age;    }    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public int getAge() {        return age;    }    public void setAge(int age) {        this.age = age;    }    @Override    public String toString() {        return name + "===========" + age;    }    @Override    public int hashCode() {        final int prime = 31;        int result = 1;        result = prime * result + age;        result = prime * result + ((name == null) ? 0 : name.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;        Person other = (Person) obj;        if (age != other.age)            return false;        if (name == null) {            if (other.name != null)                return false;        } else if (!name.equals(other.name))            return false;        return true;    }}

//Test（主类）import java.util.HashSet;import java.util.Set;public class Test {    public static void main(String[] args) {        Set<Person> set = new HashSet<Person>();        set.add(new Person("李四",3));        set.add(new Person("张三",2));        set.add(new Person("张三",2));        set.add(new Person("王五",4));        System.out.println(set.toString());    }}