I’m getting a “Required Type is Deque but provided is …” #

There are two possible issues. Make sure you haven’t accidentally imported java.util.* (or java.util.LinkedList or java.util.ArrayList). The other possible issue comes with an issue in your class signature.

Intellij is telling me “The method … of type LinkedListDeque has the same erasure as … of type Deque but does not override it.” #

You probably forgot the generic T in the implements line of your class signature (i.e. you wrote implements Deque instead of implements Deque<T>). If you used something other than T for your generic type parameter, use that instead.

Q: How do I make my arrows point to particular fields of a data structure? #

In your diagram from lecture it looked like the arrows were able to point to the middle of an array or at specific fields of a node.

A: Any time I drew an arrow in class that pointed at an object, the pointer was to the ENTIRE object, not a particular field of an object. In fact it is impossible for a reference to point to the fields of an object in Java.

Q: What does OOB stand for? #

Out of bounds.

Q: My tests pass locally but Gradescope is telling me “NullPointerException: Cannot invoke java.lang.Iterable.iterator() because this.actual is null” #

This may be caused by returning null in your toList method. Make sure that toList always returns an ArrayList, even if the Deque is empty.