练习作答

给Person类增加equals方法，使得调用indexOf()方法返回正常：

import java.util.List;
import java.util.Objects;

public class Main {
    public static void main(String[] args) {
        List<Person> list = List.of(
            new Person("Xiao", "Ming", 18),
            new Person("Xiao", "Hong", 25),
            new Person("Bob", "Smith", 20)
        );
        boolean exist = list.contains(new Person("Bob", "Smith", 20));
        System.out.println(exist ? "测试成功!" : "测试失败!");
    }
}

class Person {
    String firstName;
    String lastName;
    int age;
    public Person(String firstName, String lastName, int age) {
        this.firstName = firstName;
        this.lastName = lastName;
        this.age = age;
    }
    public boolean equals(Object o) {
        if (o instanceof Person) {
            Person p = (Person) o;
            return Objects.equals(this.firstName, p.firstName) && Objects.equals(this.lastName, p.lastName) && this.age == p.age;
        }
        return false;
    }
}