1. Announcements & Review
Last Time: Collections
ArrayList -
look up - constant time
remove, resizing, insert in the middle - expensive, time proportional to the list size
Today: a new collection
Linked List - similar operations as ArrayList, but different storage model
resizing, removal, insertion - constant time
find - proportional to list size.
Announcements
Lab 9: Inheritance Defining & using class hiearchies
Read:
R&S 11
Lecture 30: Collections Linked List

2. Linked List Storage Model
start
end
null
next
Key:
prev
node
No diriect indexing, as in arrays, so you must iterate over the list to enumerate an element
Adding at the front or the back is constant time, i.e., resizing is cheap
Lecture 30: Collections Linked List

3. Interesting LinkedList<E> Methods
size() - returns number of objects
add(Object o) - adds at end of list
get(int i) - returns ith object in the list
set(int i, Object o) - stores o at ith position in list
add(int i, Object o) - adds o at ith position, shifts other objects to the right
E remove() - removes and returns element current position, shifts elements to the left
removeFirst(), removeLast(), remove(E v), remove(int i), remove()
Lecture 30: Collections Linked List

4. Interesting LinkedList<E> Methods
E clone() - return a shallow copy of the list
Boolean addAll(LinkedList<E> c) - add collection c to end of list, return true if list changes
E peek() - return the first element without removing it from the list
Boolean hasNext(), E next() - iteration
Lecture 30: Collections Linked List

5. Lecture 30: Collections Linked List
apples
null 33 41 8
101 14
McIntosh
Red
Gala
Fuji
Golden Delicious
Linked list example declaration (same as ArrayList):
LinkedList<Items> apples = new LinkedList<Items>();
Items a = new Items(“McIntosh”, 33);
apples.add(a);
a = new Items(“Red”, 41);
apples.add(a); ...
Lecture 30: Collections Linked List

6. Iterators for LinkedList
// Basic format:
Iterator<E> itr = list.iterator();
while (itr.hasNext()) {
E element = itr.next(); // do something with the object }
// Example: Delete “Gala” apples inventory
LinkedList<Items> apples = new LinkedList<Items>();
...
Iterator<Items> i = apples.iterator();
while (i.hasNext()) {
Items item = i.next();
if (item.getName().equals(“Gala”)) {
i.remove();
} }
Lecture 30: Collections Linked List

7. Lecture 30: Collections Linked List
BlueJ
Lecture 30: Collections Linked List