Java: Avoid inserting duplicate in arraylist

Question

I am novice to java. I have an ArrayList and I want to avoid duplicates on insertion. My ArrayList is

ArrayList karList         


        

Answer 1

A set is simply a collection that can contain no duplicates so it sounds perfect for you.

It is also very simple to implement. For example:

Set mySet = new HashSet();

This would provide you a set that can hold Objects of type String.

To add to the set is just as simple:

mySet.add("My first entry!");

By definition of a set, you can add whatever you want and never run into a duplicate.

Have fun!

EDIT : If you decide you are dead-set on using an ArrayList, it is simple to see if an object is already in the list before adding it. For example:

public void addToList(String newEntry){
    if(!myList.contains(newEntry))
        myList.add(newEntry);
}

Note: All my examples assume you are using String objects but they can easily be swapped to any other Object type.