data structure in java

The files in the lab2 directory contain classes for two different types of

doubly-linked list.  The DList1 class does not use a sentinel, whereas the

DList2 class does.  The DList1 class is not circularly linked, but the DList2

class is (through the sentinel).  Compile DList1.java and DList2.java (using

"javac -g DList1.java DList2.java".)

Your task is to implement two insertFront() and two removeFront() methods--one

of each for each list class.  insertFront() and removeFront() insert or remove

an item at the beginning of a list.  Make sure your implementations work for

empty lists, one-node lists, and larger lists.

The main() methods of DList1 and DList2 include test code, which you can run

with "java DList1" and "java DList2".

Part I:  insertFront in DList1 (1 point)

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Write a method called DList1.insertFront() that inserts an int at the front of

"this" DList1.

Part II:  removeFront in DList1 (1 point)

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Write a method called DList1.removeFront() that removes the first item (and

node) from "this" DList1.

Part III:  insertFront in DList2 (1 point)

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Write a method called DList2.insertFront() that inserts an int at the front of

"this" DList2.  Your code should NOT use any "if" statements or conditionals.

Part IV:  removeFront in DList2 (2 points)

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Write a method called DList2.removeFront() that removes the first item (and

non-sentinel node) from "this" DList2.  Your code should not require separate

branches for the one-node case and the more-than-one-node case.  (You will

need one "if", to handle the zero-node case.)

Check-off

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Run the DList1 and DList2 test code.

1 point:  DList1.insertFront().

1 point:  DList1.removeFront().

1 point:  DList2.insertFront().

1 point:  DList2.removeFront().