Checking if an Array element within an ArrayList contains a certain value

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

What have tried ? Also, IMO, it will be better if you use an object, e.g. Point, instead of a 2d array (Object[]). — Bhesh Gurung
– Bhesh Gurung, Commented Apr 22, 2012 at 20:02
I recommend to change your design, instead of ArrayList<Object[]> use a Map<String, Object[]> and have a String constant MOVES to identify your 2D array — Luiggi Mendoza
– Luiggi Mendoza, Commented Apr 22, 2012 at 20:02

Cratylus · Accepted Answer · 2012-04-22 20:31:31Z

1

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.

answered Apr 22, 2012 at 20:31

Cratylus

54.3k73 gold badges222 silver badges348 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Win32 · Accepted Answer · 2012-04-22 20:06:17Z

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)

answered Apr 22, 2012 at 20:06

Win32

1,13910 silver badges12 bronze badges

Collectives™ on Stack Overflow

Checking if an Array element within an ArrayList contains a certain value

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related