How to remove duplicate objects in a List without equals/hashcode?

Question

I have to remove duplicated objects in a List. It is a List from the object Blog that looks like this:

public class Blog {
    private String title;
    priv         


        

Answer 1

If your Blog class has an appropriate equals() method defined on it, the simplest way is just to create a Set out of your list, which will automatically remove duplicates:

List blogList = ...; // your initial list
Set noDups = new HashSet(blogList)

The chances are this will work transparently with the rest of your code - if you're just iterating over the contents, for example, then any instance of Collection is as good as another. (If iteration order matters, then you may prefer a LinkedHashSet instead, which will preserve the original ordering of the list).

If you really need the result to be a List then keeping with the straightforward approach, you can just convert it straight back again by wrapping in an ArrayList (or similar). If your collections are relatively small (less than a thousand elements, say) then the apparent inefficiencies of this approach are likely to be immaterial.