java代码如何实现集合（Set）数据结构 java代码集合结构的基础编写方法​

java.util.Set

import java.util.HashSet;
import java.util.Set;

public class HashSetExample {
    public static void main(String[] args) {
        // 创建一个HashSet
        Set<String> mySet = new HashSet<>();

        // 添加元素
        mySet.add("Apple");
        mySet.add("Banana");
        mySet.add("Apple"); // 重复元素，不会被添加
        mySet.add("Orange");

        // 打印集合
        System.out.println("HashSet: " + mySet); // 输出的顺序是不确定的

        // 检查元素是否存在
        boolean containsBanana = mySet.contains("Banana");
        System.out.println("Contains Banana: " + containsBanana);

        // 删除元素
        mySet.remove("Banana");
        System.out.println("HashSet after removing Banana: " + mySet);

        // 集合大小
        System.out.println("Size of HashSet: " + mySet.size());

        // 迭代集合
        System.out.println("Iterating over HashSet:");
        for (String element : mySet) {
            System.out.println(element);
        }

        // 清空集合
        mySet.clear();
        System.out.println("HashSet after clearing: " + mySet);
    }
}

equals()

hashCode()

import java.util.HashSet;
import java.util.Set;
import java.util.Objects;

class Person {
    private String name;
    private int age;

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

    public String getName() {
        return name;
    }

    public int getAge() {
        return age;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        Person person = (Person) o;
        return age == person.age && Objects.equals(name, person.name);
    }

    @Override
    public int hashCode() {
        return Objects.hash(name, age);
    }

    @Override
    public String toString() {
        return "Person{" +
                "name='" + name + '\'' +
                ", age=" + age +
                '}';
    }
}

public class CustomObjectSetExample {
    public static void main(String[] args) {
        Set<Person> people = new HashSet<>();
        Person p1 = new Person("Alice", 30);
        Person p2 = new Person("Bob", 25);
        Person p3 = new Person("Alice", 30); // 与p1相同

        people.add(p1);
        people.add(p2);
        people.add(p3);

        System.out.println("Set of People: " + people); // 如果没有重写equals和hashCode，p3会被认为是不同的对象
        System.out.println("Size of Set: " + people.size()); // 应该输出2，而不是3
    }
}

Person

equals()

hashCode()

p1

p3

Objects.hash()

equals()

hashCode()