lesson18 - The List and Iterator interface

Overview

In this lab we are going to write a small app that will demonstrate how different collections all use an Iterator and how we can pass around a List interface.

Important Links

• Lab Overview
• Class Coding standards
• Cloning and Submitting

Objectives

• Work with the Iterators from the Java API
• Use the List interface
• Write a method that takes an Iterator as an argument
• Write your own equals and hash code method

Task 1 - Implement MyItem

In the starter code you will find a file named MyItem.java that can represent an item on a purchase order. Your task is to complete the implementation of this class. The MyItem class must implement the Item interface and must override the following methods:

• public boolean equals(Object obj)
• public int hashCode()
• public String toString()

Developing your own hashcode algorithm is a bit out of scope for this assignment so we will give it to you to use directly. This is a simple hash code that uses the properties of the class to generate a hashcode.

    @Override
    public int hashCode() {
        final int prime = 31;
        int result = 1;
        result = prime * result + ((name == null) ? 0 : name.hashCode());
        result = prime * result + ((qty == null) ? 0 : qty.hashCode());
        return result;
    }

MyItem includes a static method that you will need to implement. The parsItems method (shown below) takes an iterator that will return a string every time you call next().

    /**
     * Takes an iterator and constructs Item objects from each call to next().
     * 
     * @param items The stings that need to be parsed into Items
     * @return A List of constructed items.
     */
    public static List<Item> parseItems(Iterator<String> items) {
        return null;
    }

You will need to reference Iterator interface for details on how to work with an iterator. The two functions that you will be using are the hasNext() and next() methods. Each call to next() will return a string in the format shown below. You will need to split the string on the space character and create a new item with the resulting data.

For example, given the string steel 4lbs you would create a new MyItem object with the name property set to steel and the qty property set to 4lbs.

steel 4lbs
bolts 23lbs
aluminum 2units

Task 2 - Write Unit tests

Now that we have our class all completed out lets write some unit tests to make sure everything works correctly!

Task 3 - Manual testing

In the file App.java you will find completed code that you can use to manually test your implementation. Note that the scanner implements the Iterator interface! So we can now just pass a scanner to the parseItems method that only takes an Iterator! That is really cool and is a good example of polymorphism in action!

Task 4 - Complete the Retrospective

Once you have completed all the tasks open the file Retrospective.md and complete each section with a TODO comment.

Task 5 - Add, Commit, Push your code

Once you are finished you need to make sure that you have pushed all your code to GitHub for grading!