package com.wpr.collection;
import java.util.LinkedList;
import java.util.List;
public class HashTable<AnyType> {
private static final int DEFAULT_TABLE_SIZE = 101;
private List<AnyType>[] theList;
private int curSize;
public HashTable() {
this(DEFAULT_TABLE_SIZE);
}
public HashTable(int size) {
//构造一个质数长度的链表
this.theList = new LinkedList[nextPrime(size)];
for(int i=0;i<theList.length;i++){
theList[i]= new LinkedList<>();
}
}
/**
* 插入,如果元素已经存在,直接返回
* @param x
*/
public void insert(AnyType x){
List<AnyType> temp = theList[myHast(x)];
if(!temp.contains(x)){
temp.add(x);
if(++curSize>theList.length)
reHash();
}
}
/**
* 表的size太小,数据的长度和表长相等时重新调整表长,装填因子为1
*/
private void reHash() {
List<AnyType>[] old = theList;
theList = new LinkedList[theList.length*2];
//更新hashTable
for(int i=0;i<theList.length;i++)
theList[i]=new LinkedList<>();
curSize = 0;
for(int i=0;i<old.length;i++){
for(AnyType x:old[i])
insert(x);
}
}
public void clear(){
for(List l:theList){
l.clear();
}
}
public void remove(AnyType x){
List<AnyType> temp = theList[myHast(x)];
if(temp.contains(x)){
temp.remove(x);
curSize--;
}
}
public boolean contain(AnyType x){
List<AnyType> temp = theList[myHast(x)];
return temp.contains(x);
}
/**
* 计算数据的hash值
* @param x
* @return
*/
private int myHast(AnyType x) {
int hashValue = x.hashCode();
hashValue%=theList.length;
if(hashValue<0)
hashValue+=theList.length;
return hashValue;
}
/**
* 返回一个比size大的质数
* @param size
* @return
*/
private int nextPrime(int size) {
if(size%2==0)
size++;
while(!isPrime(size)){
size +=2;
}
return 0;
}
/**
* 判断size是否为质数
* @param size
* @return
*/
private boolean isPrime(int size) {
if(size%2==0||size==1)
return false;
if(size==2 || size==3)
return true;
for(int i=3;i<Math.sqrt(size);i+=2){
if(size%i==0)
return false;
}
return true;
}
}