用java实现的哈希表（散列表）

用java实现的一个哈希表（散列表）。只是简单实现了一些功能，想借此深入了解哈希表的具体实现。最好的学习方法还是看java源码。

public class Table{private int manyItems;private Object[] keys;private Object[] values;private boolean[] hasBeenUsed;public Table(int capacity){if(capacity <= 0){throw new IllegalArgumentException("Capacity is negative.");}keys = new Object[capacity];values =new Object[capacity];hasBeenUsed = new boolean[capacity];}/** * 判断表是否为空 * @return */public boolean isEmpty(){return manyItems == 0;}/** * 清空表 */public synchronized void clear() {if(manyItems !=0){for(int i = 0;i < values.length;i++){keys[i]=null;values[i]=null;hasBeenUsed[i]=false;}manyItems = 0;}}/** * 判断是否存在指定的关键字 * @param key * @return */public boolean containsKey(Object key) {return findIndex(key)!=-1;}public Object get(Object key) {int index = findIndex(key);if(index!=-1){return values[index];}return null;}public synchronized Object put(Object key, Object value) {int i = findIndex(hash(key));Object temp = null;if(i != -1){//表中已经存在该关键字temp = values[i];values[i] = value;//返回被替换的内容return temp;}else if(manyItems < values.length){//表中不存在该关键字且表未满i = hash(key);//检查散列码是否有冲突if(keys[i]!= null){//散列码有冲突，索引前移i = nextIndex(i);}keys[i] = key;values[i]= value;hasBeenUsed[i] = true;manyItems ++;return null;}else{//表已满throw new IllegalStateException("Table is full");}}public synchronized Object remove(Object key) {int index = findIndex(key);Object result = null;if(index!=-1){result = values[index];keys[index]= null;values[index]= null;hasBeenUsed[index]=false;manyItems --;}return result;}/** * 如果在表中找到了指定的关键字，返回指定关键字的索引。否则返回 -1. * @param key * @return */public int findIndex(Object key){int count = 0;int i = hash(key);while((count < values.length) && hasBeenUsed[i]){//分配的位置已经被使用，而且存在指定的关键字if(keys[i].equals(key)){return i;}//编辑遍历的次数，当全部元素都遍历完之后，退出遍历count++;i = nextIndex(i);}return -1;}/** * 获取散列码，大小不超过表的大小 * @param key * @return */public int hash(Object key){return Math.abs(key.hashCode())%values.length;}public int nextIndex(int index){if(index+1 == values.length){return 0;}else{return index + 1;}}/** * 判断指定的位置是否已经被使用 * @param index * @return */public boolean hasBeenUsed(int index){return hasBeenUsed[index];}/** * 返回该表中有多少对键值对。 * @return */public int size() {return manyItems;}}