ListUtil(差集、交集、并集)

 package cn.fraudmetrix.octopus.horai.biz.utils;

 import java.util.ArrayList;

 import java.util.Arrays;

 import java.util.Collections;

 import java.util.List;

 /**

  * Created by hunt on 2017/7/31.

  */

 @SuppressWarnings("all")

 public class ListUtil {

     /**

      * 求ls对ls2的差集,即ls中有，但ls2中没有的

      *

      * @param ls

      * @param ls2

      * @return

      */

     public static List diff(List ls, List ls2) {

         List list = new ArrayList(Arrays.asList(new Object[ls.size()]));

         Collections.copy(list, ls);

         list.removeAll(ls2);

         return list;

     }

     /**

      * 求2个集合的交集

      *

      * @param ls

      * @param ls2

      * @return

      */

     public static List intersect(List ls, List ls2) {

         List list = new ArrayList(Arrays.asList(new Object[ls.size()]));

         Collections.copy(list, ls);

         list.retainAll(ls2);

         return list;

     }

     /**

      * 求2个集合的并集

      *

      * @param ls

      * @param ls2

      * @return

      */

     public static List union(List ls, List ls2) {

         List list = new ArrayList(Arrays.asList(new Object[ls.size()]));

         Collections.copy(list, ls);//将ls的值拷贝一份到list中

         list.removeAll(ls2);

         list.addAll(ls2);

         return list;

     }

 }