Software Development with UML and Java 2 SDJ I2, Spring 2010

1. 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. collection.stringcollection.IStringList

3. StringListArrayBased • In the array implementation we have the following two instance variables: • private String[] collection; • private int size;

4. Linked List – single linked value next StringNode

5. 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. 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. 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. Insert a node in a linked list (step 3/3) • Step 3: Let current's next point to newNode

9. 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. 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. Linked List – circular singly linked Efficient to add and remove first – and add last Remove last is still time consuming

12. Linked List – circular doubly linked Efficient to add and remove first and last

13. Linked List – doubly linked previous next value StringDoublyNode Instance variables of the collection class • private StringDoublyNode head; • private int size;

14. Single linked implementation (StringNode)

15. Doubly linked implementation (StringDoublyNode)

16. 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.StringNodeor collection.stringcollection.StringDoublyNode