List of Lists sorting

[Nerijus]

Hi, I am having some problems sorting this one.

alist = [B, a, n, a, n, a, s]

ArrayList<Character> alist = new ArrayList<Character>();
 ArrayList<ArrayList<Character>> data = new ArrayList<ArrayList<Character>>();


       
 for(int i=0; i<list.length-1; i++){
        data.add(i, alist);
        Collections.rotate(alist, 1);   
        System.out.println(alist);
        }

after this prints:

[s, B, a, n, a, n, a]
[a, s, B, a, n, a, n]
[n, a, s, B, a, n, a]
[a, n, a, s, B, a, n]
[n, a, n, a, s, B, a]
[a, n, a, n, a, s, B]

but writes in data list this:

[a, n, a, n, a, s, B]
[a, n, a, n, a, s, B]
[a, n, a, n, a, s, B]
[a, n, a, n, a, s, B]
[a, n, a, n, a, s, B]
[a, n, a, n, a, s, B]

It's first problem, well i believe that this is becouse of the same name

alist

, but then how to do this correctly.

Other problem is that i want to sort data list in alphabet order.

I would be grateful for some help.

[Fubarable]

Your List of Lists is holding multiple Lists, but they all refer to the very same object, and for this to work, you'll need to make a new List object for each item that you'll be adding into your data List of Lists. For example

   public static void main(String[] args) {
      List<String> aList = Arrays.asList(new String[]{"a", "b", "c", "d", "e", "f"});
      List<List<String>> listOfLists = new ArrayList<List<String>>();
      
      List<String> newList = new ArrayList<String>(aList);
      listOfLists.add(newList);
      for (int i = 1; i < aList.size(); i++) {
         newList = new ArrayList<String>(newList);
         Collections.rotate(newList, 1);
         listOfLists.add(newList);
      }
      
      System.out.println(listOfLists);
      
   }

[Nerijus]

Thanks i see now this worked fine. Maybe you can give me some hint how i could sort listOfLists.

I think that this one could help:

Collections.sort(List of lists, Comparator c).

or not?

but how to write that Comparator that it would sort lists in normal order

[Fubarable]

Thanks i see now this worked fine. Maybe you can give me some hint how i could sort listOfLists.

I think that this one could help:

Collections.sort(List of lists, Comparator c).

or not?

but how to write that Comparator that it would sort lists in normal order

Yes, a Comparator should work fine. As to how, I don't know since what is "normal order"? Your Comparator will only need one method, compare. What have you tried so far?

[Nerijus]

Well now i am trying this

Collections.sort(lisOfLists, new Comparator<List<Character>>() {

                @Override
                public int compare(List<Character> o1, List<Character> o2) {
                   /* if(o1.get(0).compareTo(o2.get(0))==1){
                        
                    }*/
                   return o2.size() - o1.size();
                }

          

            });

Don't really know how to do this.
I need that first element in lisOfLists would be aList which first char in alphabet order would be the highest.

If there are 2 lists or more which first char is the same then it have to rely on the second char and so on till the end.

[Fubarable]

Why not use a simple for loop, checking each Character in one list with the other via Character's compareTo method. If not 0, then return that value.

[Nerijus]

well i don't what i am doing :D
can you help me ?

Collections.sort(data, new Comparator<List<Character>>() {

                @Override
                public int compare(List<Character> o1, List<Character> o2) {
                    int i=0;
                    while(i!=o1.size()){
                    if(o1.get(i).compareTo(o2.get(i))==0){
                        return o1.size();
                    }
                    i++;
                    }
                    return o2.size();
                }

          

            });

[Fubarable]

I have no idea why you're trying to return the size of the list since a compare method will usually return 1, 0, or -1 and size has nothing to do with it, and also, you're also not using the for loop as I suggested. But if you think through this thing logically rather than just guessing, you should be able to solve it. I'll give you a start with pseudocode:

         compare method that compares list o1 and o2 and returns and int
            since both lists are same size, for-loop through one of the lists
               compare the i-th item of each list.
               If the result isn't 0, return the result.
            end of for loop
            If we've made it this far, all items are the same, so return 0
         end of compare method

[camickr]

Maybe you can give me some hint how i could sort listOfLists

You can use Column Comparator « Java Tips Weblog.