HashSets的自定义比较

import java.util.HashSet;

class Person {
    private String name;
    private int age;

    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }

    // 重写equals()方法
    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null || getClass() != obj.getClass()) {
            return false;
        }
        Person person = (Person) obj;
        return name.equals(person.name);
    }

    // 重写hashCode()方法
    @Override
    public int hashCode() {
        return name.hashCode();
    }
}

public class Main {
    public static void main(String[] args) {
        HashSet<Person> personSet = new HashSet<>();
        personSet.add(new Person("Alice", 25));
        personSet.add(new Person("Bob", 30));
        personSet.add(new Person("Alice", 25)); // 重复元素，不会被添加进HashSet

        System.out.println(personSet.size()); // 输出：2
    }
}