快速得到两个list中不同部分的list

import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;public class TesList {public static void main(String[] args) {List<String> list = new ArrayList<String>();list.add("123");list.add("456");list.add("789");List<String> list2 = new ArrayList<String>();list2.add("123");list2.add("456");list2.add("789");list2.add("xxxx");list2.add("yyyy");List<String>list3= getDiffrent(list, list2);for (String string : list3) {System.out.println(string);}}private static List<String> getDiffrent(List<String> list1,List<String> list2) {long st = System.nanoTime();Map<String, Integer> map = new HashMap<String, Integer>(list1.size()+ list2.size());List<String> diff = new ArrayList<String>();for (String string : list1) {map.put(string, 1);}for (String string : list2) {Integer cc = map.get(string);if (cc != null){map.put(string, ++cc);continue;}map.put(string, 1);}for (Map.Entry<String, Integer> entry : map.entrySet()){if (entry.getValue() == 1){diff.add(entry.getKey());}}System.out.println("getDiffrent total times "+ (System.nanoTime() - st));return diff;}}