One Interface, Two Cost Profiles

Six things this topic established, and where each one was.

What the topic established, and which card it was on
The thing	Where
Identical methods, opposite storage, opposite costs	Two Lists With the Same Methods and Opposite Costs
Positional reads are arithmetic on one and a walk on the other	Getting the Five-Hundredth Element
Inserting at the front shifts everything on one and changes two pointers on the other	Inserting at the Front of Each
An `ArrayList` starts at zero capacity and grows by copying	What an ArrayList Does
Use `ArrayList` unless the work is genuinely at the front or middle	Which List Your Access Pattern Asks For
Remove with `removeIf` or the iterator, never through the list mid-loop	Why Removing Inside a for-each Throws

The one worth carrying: the interface tells you nothing about cost, on purpose. What decides between these two is which operation your code does most, which is a question about your code and not about the library.

Java
Java Collections
Performance