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

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

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

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

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

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

Lecture 30: Collections Linked List BlueJ Lecture 30: Collections Linked List