Double Linked$-$Lists $(100$ pts$)$

A$)$ Doubly Linked$-$List $($double linked$-$list code can be found in the "Assignment$5\_$C$"$ IntelliJ project$).$

Your task for Part A is to fully implement the "FishLinkedList" class. The FishLinkedList class is a

doubly linked$-$list that holds Fish objects. The start of the doubly linked$-$list is "head", the end is

"tail".

The fixed stack methods that need to be implemented are as follows:

private boolean contains$($Fish fish$)$

Returns true if the Fish parameter "fish" is already in the doubly linked$-$list, false if not.

public boolean addFirst$($Fish fish$)$

Adds the Fish parameter "fish" to the beginning of the linked list unless that fish is already

in the doubly linked$-$list. Return true if the Fish is added, false if the Fish was not added

because it is already in the list.

public boolean addLast$($Fish fish$)$

Adds the Fish parameter "fish" to the end of the linked list unless that fish is already in

the doubly linked$-$list. Return true if the Fish is added, false if the Fish was not added

because it is already in the list.

public boolean add$($int index, Fish fish$)$

Adds the Fish parameter "fish" to the linked list at the specified "index", unless that index

is beyond the end of the doubly linked$-$list or that fish is already in the doubly linked$-$list.

Return true if the Fish is added, false if the index is beyond the end of the doubly linked$-$

list or if it is already in the list.

public Fish removeFirst$()$

Remove and return the first Fish in the doubly linked$-$list. Return null if the list is empty.

public Fish removeLast$()$

Remove and return the last Fish in the doubly linked$-$list. Return null if the list is empty.

public Fish remove$($int index$)$

Remove and return the Fish at the specified "index". Return null if the index is beyond

the end of the doubly linked$-$list or if the list is empty.

public Fish get$($int index$)$

Return $($but do not remove$)$ the Fish at the specified "index". Return null if the index is

beyond the end of the doubly linked$-$list or if the list is empty.