CS226 -- Day 12 -- Spring 2013

SLList.java - first task is to finish this generic singly linked list



Read this tutorial on Generics and the Collections Framework in Java:
http://docs.oracle.com/javase/tutorial/index.html


Better Bag implementations: Iterators and Linked Lists

INTRODUCING ITERATORS ---------------------------------------------

Declaring Iterators w/the Java API :::::::::::::::::::::::

java.lang.Iterable<T> interface - means the class has an iterator
        /** return initialized iterator for object */
        Iterator<T> iterator();        

java.util.Iterator<T> interface - means the class is an iterator
    - abstract process of scanning through collection
    - forward motion only
    - cursor is always before the next element
    - java interface methods:
        boolean hasNext();
        T next();
        void remove();
    - eg: Scanner implements Iterator

    - bad to have multiple iterators modifying one list
        - java failsafe operation
        - conflicting remove throws ConcurrentModificationException

Using Iterators:::::::::::::::::::::::::::

foreach loop in Java 
    - processes all items in array or iterable collection
    - on arrays:
        given initialized T[] ra
        for (T item: ra)        // for i=0 to <ra.length
            do something with item    // item is ra[i]

    - with iterators: 
        given some initialized Iterable<T> set
        for (T item : set)
            do something with item


Implementing Iterators::::::::::::::::::::

Inner classes 
    - declared in class as member
    - can directly access privates in outer class
    - use Outer.this to explicitly refer to outer class member (if conflict)
    * best way to implement an Iterator for a class

Nested classes 
    - declared in class, but static
    - can access privates in outer class if passed to nested class
    - we'll use these for nodes in linked lists

EXAMPLES: Create Iterable version of Bag
    - make Bagi interface implement Iterable
    - make BagiArray implement Bagi
    - add Iterator inner class to BagiArray
    - main method shows some usage of the BagIterator
	- similarly we have BagiList, a singly linked list implementation
    	of Bagi