java - Prevent duplicate entries in arraylist

Question

Say I create some object class like so

public class thing {
        private String name; 
        private Integer num;

        public oDetails (String a, Integer b) {
            name = a;
            num = b;
        }
...gets/ sets/ etc

Now I want to create an arraylist to hold a number of this object class like so.

ArrayList<thing> myList = new ArrayList<thing>;
thing first = new thing("Star Wars", 3);
thing second = new thing("Star Wars", 1);
myList.add(first);
myList.add(second);

I would like to include some sort of logic so that in this case...when we try and add object "second" rather than add a new object to the arrayList, we add second.getNum() to first.getNum(). So if you were to iterate through the ArrayList it would be

"Star Wars", 4

I am having trouble coming up with an elegant way of handling this. And as the arraylist grows, searching through it to determine if there are duplicate name items becomes cumbersome. Can anyone provide some guidance on this?

Answer 1

If you want to have a set of unique objects, use Set instead of List.

Also, if you want to define by yourself when objects are considered equal, consider overriding the equals and hashCode methods of the class.