手写hashMap1

1. hashmap和hashtable 区别

hashtable put() get()都上锁了synchronized

可以
可以

二、代码实战

ArrayList和LinkedList 2种方式来实现
1.先定义接口

public interface MayiktMap<K,V>{
    /**
     * 集合 大小
     */
    int size();

    V put(K key, V value);

    V get(K key);

    interface Entry<K,V> {
        K getKey();

        V getValue();
    }

}

import lombok.Data;

import java.util.ArrayList;
import java.util.List;

@Data
public class ArrayListHashMap<K,V> implements MayiktMap<K,V> {
    private int size;

    private List<Node> nodes = new ArrayList<Node>();

    public int size() {
        return 0;
    }

    public V put(K key, V value) {
        Node node = getNode(key);
        if(node!=null){
            node.v = value;
            return node.getValue();
        }
        Node newNode = new Node(key, value);
        nodes.add(newNode);
        size++;
        return value;
    }


    public V get(K key) {
        return getNode(key).getValue();
    }

    private Node getNode(K key){
        for (Node node :nodes) {
            if(key.equals(node.k)){
                return node;
            }
        }
        return null;

    }

    @Data
    class Node implements Entry<K,V>{
        private K k;
        private V v;

        public K getKey() {
            return k;
        }

        public V getValue() {
            return v;
        }

        public Node(K k, V v) {
            this.k = k;
            this.v = v;
        }
    }
}

import lombok.Data;

import java.util.LinkedList;

public class LinkedListHashMap<K,V> implements MayiktMap<K,V> {

    private LinkedList<Node>[]  objects = new LinkedList[100];

    /**
     * 相同的连标存放hashcode值相同 但是对象不同
     * @return
     */


    public int size() {
        return 0;
    }

    public V put(K key, V value) {
        int index= key.hashCode()%objects.length;
        LinkedList<Node> nodes = objects[index];
        if(nodes == null){
            nodes = new LinkedList<Node>();
        }
        nodes.add(new Node(key, value));
        objects[index] = nodes;
        return value;
    }

    public V get(K key) {
        int index= key.hashCode()%objects.length;
        LinkedList<Node> nodes = objects[index];
        for (Node node :nodes) {
            if(key.equals(node.k)){
                return node.v;
            }        }
        return null;
    }

    @Data
    class Node implements Entry<K,V>{
        private K k;
        private V v;

        public K getKey() {
            return null;
        }

        public V getValue() {
            return null;
        }

        public Node(K k, V v) {
            this.k = k;
            this.v = v;
        }
    }
}

public class Test001 {
    public static void main(String[] args) {
        ArrayListHashMap arrayListHashMap = new ArrayListHashMap<String,String>();
        arrayListHashMap.put("mayi","kt");
        System.out.println(arrayListHashMap.get("mayi"));

        LinkedListHashMap<Object, String> linkedListHashMap = new LinkedListHashMap<Object, String>();
        linkedListHashMap.put("a","mayi");
        linkedListHashMap.put(97,"mayi2");
        System.out.println(linkedListHashMap.get("a"));
        System.out.println(linkedListHashMap.get(97));

    }
}