检查ArrayList中的Array元素是否包含特定值

Question

I have this ArrayList - ArrayList<Object[]> tree ...

I also have this Array - Object[] move ...that has a size of 2.

In my program a unique 2D array is added to move[0] and an integer to move[1] . This array is then added to the ArrayList then the process is repeated so I have a list of 'moves'.

My problem is I am unsure how to find the arrays ('moves') within the ArrayList ('tree') that contain a certain value in the move[1] element only - as the move[0] element will be unique everytime.

I then want to make an array/list of all of the matches. For example, an array that contains all of the move[0] values that match up to the move[1] value of 3 . So I would be left with an array/list of 2D arrays that contain the required moves.

Thanks, Matt

Answer 1

The simplest way is just iterating through your tree object and building a new ArrayList with the found matches, but this will take time linear to the size of that tree . If you're looking for speed, then you could maintain a HashMap<Integer, ArrayList<Object[]>> , where the keys are the integers you store in move[1] , and the value is a list of all the moves that have that key, so retrieving that list can be done in O(1)

Answer 2

It seems to me that what you need is a key-value data structure and you have chosen a rather odd way to implement it.
You should use either a HashTable if you can not use generics (you are in an old jdk for some reason) or use a HashMap using types to enforce type safety.