1. Page 1 – Spring 2010Steffen Vissing Andersen Software Development with UML and Java 2 SDJ I2, Spring 2010 Agenda – Week 8 Linked List (a reference based list implementation) IStringList implementations StringListArrayBased StringListReferenceBased

2. Page 2 – Spring 2010Steffen Vissing Andersen collection.stringcollection.IStringList

3. Page 3 – Spring 2010Steffen Vissing Andersen StringListArrayBased In the array implementation we have the following two instance variables:  private String[] collection;  private int size;

4. Page 4 – Spring 2010Steffen Vissing Andersen Linked List – single linked StringNode valuenext

5. Page 5 – Spring 2010Steffen Vissing Andersen Insert a node in a linked list Insert a node with value = "X" at index 3, i.e. between "C" and "D": myList.add("X", 3); Step 1: Find the node at index 2 (node just before index 3) Step 2: Create a node with value = "X" and next pointing to the node at index 3 Step 3: Let the node at index 2 point to the new node

6. Page 6 – Spring 2010Steffen Vissing Andersen Insert a node in a linked list (step 1/3) Step 1: find the node just before where to insert (insert at index 0 is a special case!) step 1.0: create a node reference current step 1.1: let current reference what head is referencing (the first node) step 1.2: let current reference the next node (the second node) step 1.3: let current reference the next node (the third node)... until current references the node just before where to insert

7. Page 7 – Spring 2010Steffen Vissing Andersen Insert a node in a linked list (step 2/3) Step 2: Create a new node with value = "X" and pointing to current 's next

8. Page 8 – Spring 2010Steffen Vissing Andersen Insert a node in a linked list (step 3/3) Step 3: Let current 's next point to newNode

9. Page 9 – Spring 2010Steffen Vissing Andersen Linked List – single linked Insert and remove at index 0 are special cases Insert and remove at index 0 are now treated just like any other cases (no special cases)

10. Page 10 – Spring 2010Steffen Vissing Andersen Linked List – singly linked, head or tail reference add(String) adds at the end of the list  time consuming Efficient to add and remove last Add and remove first are now time consuming

11. Page 11 – Spring 2010Steffen Vissing Andersen Linked List – circular singly linked Efficient to add and remove first – and add last Remove last is still time consuming

12. Page 12 – Spring 2010Steffen Vissing Andersen Linked List – circular doubly linked Efficient to add and remove first and last

13. Page 13 – Spring 2010Steffen Vissing Andersen Linked List – doubly linked StringDoublyNode previous value Instance variables of the collection class private StringDoublyNode head; private int size; next

14. Page 14 – Spring 2010Steffen Vissing Andersen Single linked implementation (StringNode)

15. Page 15 – Spring 2010Steffen Vissing Andersen Doubly linked implementation (StringDoublyNode)

16. Page 16 – Spring 2010Steffen Vissing Andersen Exercises StringListReferenceBased collection.stringtcollection.IStringList (interface already given) collection.stringcollection.StringListReferenceBased Version1: use a single linked list with a head reference and size Version2: use a single linked list with a tail reference and size Note: if you use methods with an index then the internal representation is reversed, e.g. Index i is stored in index size-i-1 Version3: use a single linked list with a dummy node, a head reference and size Version4: use a circular single linked list with a tail reference and size Version5: use a circular doubly linked list with a head reference and size (it is optional if it has a dummy node or not) collection.stringcollection.StringNode or collection.stringcollection.StringDoublyNode