인프런 커뮤니티 질문&답변

import collection.set.member.Member;

public class MyHashSetV2Main2 {

    public static void main(String[] args) {
        MyHashSetV2 set = new MyHashSetV2(10);
        Member hi = new Member("hi");
        Member jpa = new Member("JPA"); // 대문자 주의!
        Member java = new Member("java");
        Member spring = new Member("spring");

        System.out.println("hi.hashCode() = " + hi.hashCode());
        System.out.println("jpa.hashCode() = " + jpa.hashCode());
        System.out.println("java.hashCode() = " + java.hashCode());
        System.out.println("spring.hashCode() = " + spring.hashCode());

        set.add(hi); // Member 타입의 인스턴스를 myHashSetV2에 넣음.
        set.add(jpa);
        set.add(java);
        set.add(spring);
        System.out.println("set = " + set);

        //검색
        Member searchValue = new Member("JPA");
        boolean result = set.contains(searchValue);
        System.out.println("hi.contains(" + searchValue + ") = " + result);

    }
}

import java.util.Objects;

public class Member {

    private final String id;

    public Member(String id) {
        this.id = id;
    }

    public String getId() {
        return id;
    }

    @Override
    public boolean equals(Object object) {
        if (this == object) return true;
        if (object == null || getClass() != object.getClass()) return false;
        Member member = (Member) object;
        return Objects.equals(id, member.id);
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(id);
    }
}

import java.util.Arrays;
import java.util.LinkedList;

public class MyHashSetV2 {

    static final int DEFAULT_INITIAL_CAPACITY = 16;

    private LinkedList<Object>[] buckets;
    private int size;
    private int capacity = DEFAULT_INITIAL_CAPACITY;

    public MyHashSetV2() {
        initBuckets();
    }

    public MyHashSetV2(int capacity) {
        this.capacity = capacity;
        initBuckets();
    }

    private void initBuckets() {
        buckets = new LinkedList[capacity];
        for (int i = 0; i < capacity; i++) {
            buckets[i] = new LinkedList<>();
        }
    }

    public boolean add(Object value) {
        LinkedList<Object> bucket = buckets[hashIndex(value)];
        if (bucket.contains(value)) {
            return false;
        }

        bucket.add(value);
        size++;
        return true;
    }

    public boolean remove(Object value) {
        LinkedList<Object> bucket = buckets[hashIndex(value)];
        boolean removeResult = bucket.remove(value);
        if (removeResult) {
            size--;
            return true;

        }

        return false;
    }

    public boolean contains(Object value) {
        int hashIndex = hashIndex(value);
        LinkedList<Object> bucket = buckets[hashIndex];
        return bucket.contains(value);

    }

    private int hashIndex(Object value) {
        return Math.abs(value.hashCode()) % capacity;
    }

    public int getSize() {
        return size;
    }

    @Override
    public String toString() {
        return "MyHashSetV2{" +
                "buckets=" + Arrays.toString(buckets) +
                ", size=" + size +
                ", capacity=" + capacity +
                '}';
    }
}

Member 클래스에 hashCode 오버라이딩도 새로 해봤는데 다르게 나옵니다 ㅠㅠ

Member클래스의 재정의한 hashCode() 의 구현 코드를 보면

@Override public int hashCode() { return Objects.hashCode(id); }

return Objects.hashCode()로 되어있습니다.

return Objects.hash()로(=강의코드) 확인해보시겠어요?

추가로 아래 링크도 참고해주세요 😀

https://www.inflearn.com/questions/1266776/generate로-hash-생성시-hash-와-hashcode