CODEWITHSUNDEEP
javaandroidsortingarraylist
laaptu
laaptu

Reputation: 2973

Android/Java how to efficiently use multiple comparator in an ArrayList

I have a Java class named Friend

public class Friend {   
    public String friendsUserName;
    public boolean isFavorite;
    public boolean isFriend;
}

I get Json file from the server containing JsonArray of this class Friend. I use Gson class to parse and map the Json to the ArrayList<Friend>.I have to sort the array in following manner

  1. Top level elements are Friend who are isFavorite and isFriend
  2. Then the ArrayList contains remaining Friend who are only isFriend
  3. Finally the ArrayList contains Friend where isFriend is False.

So for that I can use the method described on this ComparatorChain

Or I can use the following way to properly sort the ArrayList<Friend>

 public ArrayList<Friend> friendsList;
 public void sortArrayList() {
    ArrayList<Friend> favoriteList = new ArrayList<Friend>();
    ArrayList<Friend> friendOnlyList = new ArrayList<Friend>();
    ArrayList<Friend> nonFriendList = new ArrayList<Friend>();

    for (int length = friendsList.size(), i = length - 1; i >= 0; i--) {
        Friend friend = friendsList.get(i);
        if (friend.isFriend) {
            if (friend.isFavorite) {
                favoriteList.add(friend);
            } else {
                friendOnlyList.add(friend);
            }
        } else {
            nonFriendList.add(friend);
        }
        friendsList.remove(i);
    }
    addAllAndClear(favoriteList);
    favoriteList = null;

    addAllAndClear(friendOnlyList);
    friendOnlyList = null;
    addAllAndClear(nonFriendList);
    nonFriendList = null;

}

public void addAllAndClear(ArrayList<Friend> updatedList) {
    Collections.sort(updatedList, nameComparator);
    friendsList.addAll(updatedList);
    updatedList.clear();
    updatedList = null;

}

    Comparator<Friend> nameComparator = new Comparator<FriendListResponse.Friend>() {
    @Override
    public int compare(Friend lhs, Friend rhs) {
        return lhs.friendsUserName.compareTo(rhs.friendsUserName);
    };
};

Efficiency wise which should I follow the ComparatorChain or my own method. I am developing this for Android platform,so Memory Management and Efficiency is of topmost priority. P.S. I am no good at using tools to compare Efficiency.

Upvotes: 0

Views: 145

Answers (2)

Unlink
Unlink

Reputation: 993

In your class Friend implement Comparable interface and then use Collections.sort()

Or as @vipul mittal suggest

Comparator may look like

Comparator<Friend> favoriteComparator = new Comparator<FriendListResponse.Friend>() {
    @Override
    public int compare(Friend lhs, Friend rhs) {
        int i=0,j=0;
        if(lhs.isFavorite() && lhs.isFriend())
           i++;
        if(lhs.isFriend())
           i++;
        if(rhs.isFavorite() && rhs.isFriend())
           j++;
        if(rhs.isFriend())
           j++; 

        if (i==j) {
            return lhs.friendsUserName.compareTo(rhs.friendsUserName);
        }
        else {
            return i-j;
        }
    };
};

Upvotes: 2

vipul mittal
vipul mittal

Reputation: 17401

Try following comparator:

Comparator<Friend> favoriteComparator = new Comparator<FriendListResponse.Friend>() {
    @Override
    public int compare(Friend lhs, Friend rhs) {
        int i=0,j=0;
        if(lhs.isFavorite()&&lhs.isFriend())
           i++;
        if(lhs.isFriend())
           i++;
        if(rhs.isFavorite()&&rhs.isFriend())
           j++;
        if(rhs.isFriend())
           j++; 
        return i-j;
    };
};

While sorting:

Collections.sort(friendsList,favoriteComparator);

Upvotes: 2

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