简单手写HashMap源码_hashmap 菜鸟教程

public class ExtHashMap {

	LinkedList[] tables = new LinkedList[990];
	private int size;

	public void put(Object key, Object value) {
		// 创建ExtEntry对象
		ExtEntry extEntry = new ExtEntry(key, value);
		// 使用hashCode()取余,获取索引位置
		int hash = key.hashCode() % tables.length;
		// 防止hash有负数
		hash = hash < 0 ? -hash : hash;
		// 获取数组的hash元素
		LinkedList mapLinkedList = tables[hash];
		if (mapLinkedList == null) {
			// 如果没有LinkedList
			LinkedList linkedList = new LinkedList();
			tables[hash] = linkedList;
			linkedList.add(extEntry);
		} else {
			// 判断Key是否已经存在
			Object existEntry = get(key);
			if (existEntry == null) {
				// 如果existEntry不存在直接往链表后面插入
				mapLinkedList.add(extEntry);
			} else {

			}

		}
	}

	public Object get(Object key) {
		// 使用hashCode()取余,获取索引位置
		int hash = key.hashCode() % tables.length;
		// 防止hash有负数
		hash = hash < 0 ? -hash : hash;
		LinkedList linkedList = tables[key.hashCode() % tables.length];
		for (int i = 0; i < linkedList.size(); i++) {
			ExtEntry extEntry = (ExtEntry) linkedList.get(i);
			if (extEntry.key.equals(key)) {
				return extEntry.value;
			}
		}
		return null;
	}

	public static void main(String[] args) {
		ExtHashMap extMap = new ExtHashMap();
		extMap.put("a", "yushengjun");
		extMap.put("b", "zhangsan");
		extMap.put("c", "liuli");
		extMap.put("c", "644064779");
		System.out.println(extMap.get("c"));

	}

}

class ExtEntry {

	Object key;
	Object value;

	public ExtEntry(Object key, Object value) {
		super();
		this.key = key;
		this.value = value;
	}

	public Object getKey() {
		return key;
	}

	public void setKey(Object key) {
		this.key = key;
	}

	public Object getValue() {
		return value;
	}

	public void setValue(Object value) {
		this.value = value;
	}

}
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HashMap数据结构