Java手写简易版HashMap（存储+查找）

HashMap的基本结构

package com.liuyuhe;

public class Node {
	int hash;
	Object key;
	Object value;
	Node next;
}

package com.liuyuhe;

public class MyHashMap {
	Node[] table; //位桶数组
	int size;	 //存放键值对的个数
	public MyHashMap() {
		table=new Node[16];
	}
	
}

put()方法存储键值对

	public void put(Object key,Object value) {
		Node newNode = new Node();
		newNode.hash=myHash(key.hashCode(),table.length);
		newNode.key=key;
		newNode.value=value;
		newNode.next=null;
		Node temp = table[newNode.hash];
		Node iterLast=null;
		if(temp==null) {
			table[newNode.hash]=newNode;
		}else {
			while(temp!=null) {
				if(temp.key.equals(key)) {
					temp.value=value;
					return;
				}else {
					iterLast=temp;
					temp=temp.next;
				}
			}
			iterLast.next=newNode;
		}
		++size;
	}
	public int myHash(int v,int length) {
		System.out.println("hash in myHash: "+(v&(length-1)));
		return v&(length-1);
	}
	

重写toString()方法打印Map内容

@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("{");
		boolean isFirst=true;
		//遍历数组
		for(int i=0;i<table.length;++i) {
			//遍历链表
			Node temp = table[i];
			while(temp!=null) {
				if(isFirst) {
					isFirst=false;
					sb.append(temp.key+":"+temp.value);
				}else {
					sb.append(","+temp.key+":"+temp.value);
				}
				temp=temp.next;
			}
		}
		sb.append("}");
		return sb.toString();
	}

get()方法查找键值对

public Object get(Object key) {
		int hash=myHash(key.hashCode(),table.length);
		Object value=null;
		if(table[hash]!=null) {
			Node temp=table[hash];
			while(temp!=null) {
				if(temp.key.equals(key)) {
					value=temp.value;
					break;
				}else {
					temp=temp.next;
				}
			}
		}
		return value;
	}

增加泛型（完整代码）

package com.liuyuhe;

public class Node<K,V> {
	int hash;
	K key;
	V value;
	Node next;
}

package com.liuyuhe;

public class MyHashMap<K,V> {
	Node[] table; //位桶数组
	int size;	 //存放键值对的个数
	public MyHashMap() {
		table=new Node[16];
	}
	public void put(K key,V value) {
		Node newNode = new Node();
		newNode.hash=myHash(key.hashCode(),table.length);
		newNode.key=key;
		newNode.value=value;
		newNode.next=null;
		Node temp = table[newNode.hash];
		Node iterLast=null;
		if(temp==null) {
			table[newNode.hash]=newNode;
		}else {
			while(temp!=null) {
				if(temp.key.equals(key)) {
					temp.value=value;
					return;
				}else {
					iterLast=temp;
					temp=temp.next;
				}
			}
			iterLast.next=newNode;
		}
		++size;
	}
	@SuppressWarnings("unchecked")
	public V get(K key) {
		int hash=myHash(key.hashCode(),table.length);
		V value=null;
		if(table[hash]!=null) {
			Node temp=table[hash];
			while(temp!=null) {
				if(temp.key.equals(key)) {
					value=(V)temp.value;
					break;
				}else {
					temp=temp.next;
				}
			}
		}
		return value;
	}
	public int myHash(int v,int length) {
		System.out.println("hash in myHash: "+(v&(length-1)));
		return v&(length-1);
	}
	@Override
	public String toString() {
		StringBuilder sb = new StringBuilder();
		sb.append("{");
		boolean isFirst=true;
		//遍历数组
		for(int i=0;i<table.length;++i) {
			//遍历链表
			Node temp = table[i];
			while(temp!=null) {
				if(isFirst) {
					isFirst=false;
					sb.append(temp.key+":"+temp.value);
				}else {
					sb.append(","+temp.key+":"+temp.value);
				}
				temp=temp.next;
			}
		}
		sb.append("}");
		return sb.toString();
	}
}