Description
The task of this project is to implement in Java a red-black tree data structure. However, the tree
will be simplified – you only need to support insertion, not deletion.
Specification
The project must implement the following specification exactly, including all identifier names,
method signatures, the presence or absence of exceptional behavior, etc. That being said,
anything not clearly indicated by the UML diagram(s) or explicitly stated in the description is left
up to your discretion. You may also add private helper methods or additional fields as necessary.
Structure
Note that a box with a dashed border over the top right of a class entity denotes a generic type
parameter. In this case, the red-black tree class has a generic type named E that extends
Comparable – you may choose whether or not to make Node generic as well. The
Comparable interface is located in the java.lang package, so it is not necessary to
import it. Finally, for this project you should locate your code in the default package.
Behavior
insert should insert the given element into the tree at the correct position, and then rebalance
the tree if necessary. The correct position is defined by the properties of a binary search tree,
and the rebalancing procedure should enforce the properties of a red-black tree. Regarding input
validation, insert should immediately throw a NullPointerException with a descriptive
message if the given element is null. Alternatively, if the given element is a duplicate of an
element already in the tree, then insert should not insert the given element. The return value
should indicate whether the given element was inserted into the tree or not.
Two elements are considered duplicates iff (if and only if) they compare equal to each other using
the compareTo method. Likewise, the ordering of any two elements for the purposes of
insertion and rebalancing is given by the same method.
contains should return whether the tree contains any element that compares equal to the
given object using the compareTo method of the object. This means that you should always
do object.compareTo(element) but never do element.compareTo(object).
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However, if the given object is null, then contains should not throw an exception but rather
should return false.
toString should override the eponymous method of Object and return a string representing
the in-order traversal of this tree. The returned string should be the ordered concatenation of
invoking the toString method of each element in the traversal, where every two adjacent
elements should be separated by a single tab character (“\t”). If an element is located in a red
node, then it should be preceded by a single asterisk character (“*”) in the output string.
Otherwise, an element located in a black node should not be preceded by an asterisk. An
example of the output is as follows (assuming that the elements are of type Integer):
2 *5 30 47 *60
It is entirely optional, but it may make your life easier to use a StringJoiner and/or to
implement Node#toString() as well.
The color field of the node class should be assigned and evaluated using the RED and BLACK
constants of the enclosing tree class. This means that you should always do color = BLACK
or if(color == RED) but never do color = true or if(!color).
Submission
Submit the following items on eLearning before 11:59PM on Sunday, October 22
nd, 2017:
1. README.txt
This should identify who you are (name, NetID, etc.), which project you are submitting,
what files comprise your project, how you developed and compiled your project (e.g.
what IDE or text editor, which version of Java, what compiler options, etc.), and any other
information you believe the grader should know or you want the grader to know.
2. RedBlackTree.java
This should be the only source code file that you submit. It should not include a main
method, since it is intended to be used like library code. (that is also how it will be tested)
The source code should include an appropriate Javadoc for every public method and class.
Both items should be submitted as a single zipped file named with your lowercase NetID. The
file structure should resemble the following example:
*– abc123789.zip
|– README.txt
|– RedBlackTree.java
Evaluation
This project will be evaluated primarily according to the correctness of your implementation of
the red-black tree insertion and rebalancing algorithm, and secondarily according to the stability
of your implementation and its faithfulness to the specification. It is of utmost importance that
you exactly adhere to the structural specifications since your code must be compatible with a
standardized test suite. Finally, bonus points may be awarded for exceptional code quality, which
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comprises engineering and design (e.g. modularity), documentation and comments (e.g.
Javadoc), and style and layout (e.g. visually grouping lines into logical “paragraphs”).
The rubric is as follows:
Category Weight
insert 70%
contains 20%
toString 10%
Your source code should include a suitable Javadoc for every public method and class.
Commentary
The specification for this project emulates several conventions used in the actual Java standard
library (with appropriate simplifications). For example, the TreeSet class is a red-black tree
that uses RED and BLACK boolean constants exactly as specified here in order to more efficiently
simulate a binary enum without sacrificing the expressive power of an enum.
