Why are dynamic arrays called ArrayLists in Java?

Question

The point of Java's ArrayLists is that they adjust their length automatically whenever items are inserted or deleted. If I understand it correctly, ArrayLists are wrappers around primitive arrays.

I was taught that:

• arrays are data structures that offer random access in O(1) but can do insertion and deletion only in O(n), while
• lists offer insertion and deletion in O(1) but provide random access only in O(n),

meaning that a data structure can't be an array and a list at the same time.

Why then does Java call it “ArrayList” – isn't that an oxymoron? (Wouldn't “DynamicArray” be more appropriate?) Or do ArrayLists actually have a “lists trope”?

Answer 1

Peanuts are neither a pea, nor a nut. What's up with that?

My point is that naming isn't required to follow whatever rule you are imagining. An ArrayList is not an array, and not a list. It has some aspects in common with an array, and some aspects with a list, but it is not identical with either. That is fine. It is still a fine name.