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

You need to use any Set implementation, e.g you can use HashSet. If you want to add custom object kar into your HashSet, you need to override equals and hashcode method. You can read more about equals and hashcode, see