gitguddy / 02-classes-interfaces

This is an assignment to the class Programmieren 3 at the University of Applied Sciences Rosenheim.

Assignment 2: Classes and interfaces revisited

In this assignment we'll be looking at

• static and regular inner classes
• anonymous classes
• lambda expressions and @FunctionalInterface by implementing a basic linked list.

A linked list consists of a controller (the list class) and elements that contain the actual payload (the container or element class). The controller class maintains a reference to the first list element (head), and every element points to its successor (or to a null value, if it's the last). The following UML shows all classes of this assignment (including the interfaces java.util.Iterator<T> and java.lang.Iterable<T>; we'll cover ).

Note: the concept of an iterator will be discussed in detail in a few weeks.

Setup

1. Create a fork of this repository.
2. Clone your fork to get a local working copy.
3. Import the project to your IDE (choose Gradle project)

Static and regular inner classes

1. What is a static class?
   • Refresh your knowledge on UML (e.g. here)
   • What's the difference between a regular inner and static inner class?
   • Can you think of some use cases for both?
2. Implement Element as static inner class of SimpleListImpl.
   • Why is this class static, and ideally private?
3. Implement the Iterator interface as inner class of SimpleListImpl.
   • Why is it helpful to make this class non-static?
4. Add the Iterable interface to your SimpleListImpl, and implement the required methods.
   • Why is implementing the Iterable interface essential for a (good) list implementation? (Hint: Check the test cases!)
   • Are there any language definition constraints to this?

Anonymous (inner) classes and lambda expressions

1. Implement the filter method for your SimpleListImpl class (see SimpleFilter interface).
2. Check the given test suite for an example on
   • how to use an anonymous class with an interface.
   • how an anonymous class can be replaced by a lambda expression.
3. Add some test methods and implement another filter logic (e.g. every third number, or any number smaller than a certain value).
4. Review anonymous classes and lambdas.
   • Lambda expressions look very convenient; can you think of a scenario where they should not be used?
   • Recall how scoping works for anonymous (inner or local) classes; can you think of a scenario where to avoid them?