集合操作
package com.ad.web.servlet.common;
import java.util.Collection;
import java.util.HashMap;
import java.util.LinkedList;
import java.util.Map;
public class CollectionUtil
{
/**
* 不允许实例化
*/
private CollectionUtil() {
}
/**
* 获取两个集合的不同元素
* @param collmax
* @param collmin
* @return
*/
@SuppressWarnings("unchecked")
public static Collection getDiffent(Collection collmax,Collection collmin){
//使用LinkeList防止差异过大时,元素拷贝
Collection csReturn = new LinkedList();
Collection max = collmax;
Collection min = collmin;
//先比较大小,这样会减少后续map的if判断次数
if(collmax.size()<collmin.size())
{
max = collmin;
min = collmax;
}
//直接指定大小,防止再散列
Map<Object,Integer> map = new HashMap<Object,Integer>(max.size());
for (Object object : max) {
map.put(object, 1);
}
for (Object object : min) {
if(map.get(object)==null)
{
csReturn.add(object);
}else{
map.put(object, 2);
}
}
for (Map.Entry<Object, Integer> entry : map.entrySet()) {
if(entry.getValue()==1)
{
csReturn.add(entry.getKey());
}
}
return csReturn;
}
/**
* 获取两个集合的相同元素
* @param collmax
* @param collmin
* @return
*/
@SuppressWarnings("unchecked")
public static Collection getSame(Collection collmax,Collection collmin){
//使用LinkeList防止差异过大时,元素拷贝
Collection csReturn = new LinkedList();
Collection max = collmax;
Collection min = collmin;
//先比较大小,这样会减少后续map的if判断次数
if(collmax.size()<collmin.size())
{
max = collmin;
min = collmax;
}
//直接指定大小,防止再散列
Map<Object,Integer> map = new HashMap<Object,Integer>(max.size());
for (Object object : max) {
map.put(object, 1);
}
for (Object object : min) {
if(map.get(object)!=null)
{
csReturn.add(object);
}
}
return csReturn;
}
}
