Collection Interface vs arrays

Question

We are learning about the Collection Interface and I was wondering if you all have any good advice for it\'s general use? What can you do with an Collection that you cannot

Answer 1

The details are in the sub interfaces of Collection, like Set, List, and Map. Each of those types has semantics. A Set typically cannot contain duplicates, and has no notion of order (although some implementations do), following the mathematical concept of a Set. A List is closest to an Array. A Map has specific behavior for push and get. You push an object by its key, and you retrieve with the same key.

There are even more details in the implementations of each collection type. For example, any of the hash based collections (e.g. HashSet, HasMap) are based on the hashcode() method that exists on any Java object.

You could simulate the semantics of any collection type based of an array, but you would have to write a lot of code to do it. For example, to back a Map with an array, you would need to write a method that puts any object entered into your Map into a specific bucket in the array. You would need to handle duplicates. For an array simulating a Set, you would need to write code to not allow duplicates.