JAVA fill a temporary Arraylist with objects and then add it into a ArrayList which consists of arrayLists

Question

I iterate through an Array which consists of objects. I want to find certain parts of this array in which the same specific objects follow eachother.

[a,b,c,#,#,#,h,g,a,#,#,s,#.h] --> I want to find #,#,# and #,# (# is the specific object)

I already figured out how to do this: If I find a '#' I will add this object to a temporary ArrayList. If the next object is a '#' too, I will add it aswell, otherwise I clear the tmplist, because it is a single '#'. If the next object is not a # but the tmplist is bigger than 1 i want to add the tmplist to a 2d ArrayList (An ArrayList which consists of ArrayLists) and clear the tmplist so I can find other parts.

Here is my problem: If i do this the the 2d arraylist does not consist of deepcopys of the templists--> The 2d arraylist consist of empty lists, because I clear the tmplist after every found "pattern". How can I fix this?

Some code which might explain it better:

List<Object> tmplist = new ArrayList<Object>();
   for (int i = 0; i<array.length(); i++) {
       if (array[i].equals(#)) {
          tmplist.add(array[i]);
              if (!array[i+1].equals(#) && tmplist.size() < 2){
                  tmplist.clear();
              } else if (!array[i+1].equals(#) && tmplist.size() > 1) {
                   pattern.add(tmplist);
                   tmplist.clear();
              } 
       }
   }
   //pattern is the 2d ArrayList (ArrayList which consists of ArrayLists)

Answer 1

if your 2d ArrayList is : result

do

 result.add(new ArrayList<>(tmpList));

By doing this, you are not adding the tmpList itself but a new list with the values of tmpList. So even If you do tmpList.clear() it will not affect the arraylist in your result.

Answer 2

Instead of doing tmplist.clear() do tmplist = new ArrayList<>() so you're working with a different List instance each time.