java代码怎样实现哈希表及解决哈希冲突 java代码哈希表结构的实用实现技巧​

HashMap

public class SimpleHashMap<K, V> {

    private static final int DEFAULT_CAPACITY = 16;
    private LinkedList<Entry<K, V>>[] table;
    private int size;

    public SimpleHashMap() {
        this(DEFAULT_CAPACITY);
    }

    public SimpleHashMap(int capacity) {
        table = new LinkedList[capacity];
        size = 0;
    }

    private int hash(K key) {
        return Math.abs(key.hashCode()) % table.length;
    }

    public void put(K key, V value) {
        int index = hash(key);
        if (table[index] == null) {
            table[index] = new LinkedList<>();
        }

        LinkedList<Entry<K, V>> list = table[index];
        for (Entry<K, V> entry : list) {
            if (entry.key.equals(key)) {
                entry.value = value; // 更新值
                return;
            }
        }

        list.add(new Entry<>(key, value));
        size++;
    }

    public V get(K key) {
        int index = hash(key);
        if (table[index] != null) {
            LinkedList<Entry<K, V>> list = table[index];
            for (Entry<K, V> entry : list) {
                if (entry.key.equals(key)) {
                    return entry.value;
                }
            }
        }
        return null;
    }

    public void remove(K key) {
        int index = hash(key);
        if (table[index] != null) {
            LinkedList<Entry<K, V>> list = table[index];
            list.removeIf(entry -> entry.key.equals(key));
            size--;
        }
    }

    public int size() {
        return size;
    }

    private static class Entry<K, V> {
        K key;
        V value;

        public Entry(K key, V value) {
            this.key = key;
            this.value = value;
        }
    }

    public static void main(String[] args) {
        SimpleHashMap<String, Integer> map = new SimpleHashMap<>();
        map.put("apple", 1);
        map.put("banana", 2);
        map.put("cherry", 3);

        System.out.println("apple: " + map.get("apple")); // 输出 1
        System.out.println("banana: " + map.get("banana")); // 输出 2
        System.out.println("cherry: " + map.get("cherry")); // 输出 3

        map.remove("banana");
        System.out.println("banana: " + map.get("banana")); // 输出 null
        System.out.println("Size: " + map.size()); // 输出 2
    }
}

Entry

table

hash

put

get

remove

hashCode()

hashCode()