What are the differences between HashSet and ArrayList in Java?

What are the differences between HashSet and ArrayList in Java?

HashSet and ArrayList are both part of Java's collection framework, but they serve different purposes. HashSet is used for storing unique elements and does not maintain any order, while ArrayList allows duplicate elements and maintains the order of insertion.

Can you explain the performance differences between them?

Sure! HashSet generally offers constant time performance for basic operations like add, remove, and contains, while ArrayList has a linear time complexity for these operations, especially when searching for elements.

When should I use HashSet instead of ArrayList?

You should use HashSet when you need to ensure that all elements are unique and when you don't care about the order of elements. It's also preferable for faster lookups.

Are there any scenarios where ArrayList is better?

Yes, ArrayList is better when you need to maintain the order of elements or when you need to access elements by their index frequently.