去重 : 去除ArrayList<Object>里面的重复记录

针对基础类型:

ArrayList<String> result = new ArrayList<String>();
for(String s: sources){
    if(Collections.frequency(reslut, s) < 1) result.add(s);
}

LinkedHashSet<String> set = new LinkedHashSet<String>(rules);
ArrayList<String> newRules = new ArrayList<String>(set);

针对对象类型:
去除ArrayList<Object>里面的重复记录 http://www.cnblogs.com/jizha/p/java_arraylist_duplicate.html

/**
  * 将列表中重复的用户移除，重复指的是userid相同
  * @param userList
  * @return
  */
 public ArrayList<UserInfo> removeDuplicteUsers(ArrayList<UserInfo> userList){
      Set<UserInfo> s= new TreeSet<UserInfo>(new Comparator<UserInfo>(){

           @Override
           public int compare(UserInfo o1, UserInfo o2) {
                return o1.userId.compareTo(o2.userId);
           }

      });

      s.addAll(userList);
      return new ArrayList<UserInfo>(s);
 }