What data type is this?

Question

I have a list of items I am adding to, however this special list will delete anything past a given capacity. Note the order is maintained.

For the life of me, I can't think of the name of such a construct.

Consider

data = new SpecialListType(3); // set capacity to 3

data.Add("A");
data.Add("B");
data.Add("C");
data.Add("D");

data.Dump(); // returns {"B", "C", "D"}

What is this? Some form of a Set or Buffer? And is there a framework implementation of this in Java and .NET?

Answer 1

It's a bounded queue (a first-in-first-out queue with a fixed capacity).

This particular queue always allows addition of elements and silently remove head element for newly added element (when full).

In Java there is the CircularFifoQueue that works exactly that way (see also Size-limited queue that holds last N elements in Java).

For .NET you'd take a look at:

• Limit size of Queue in .NET?
• Fixed size queue which automatically dequeues old values upon new enques