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Software Specification and Design
Engi 9874, 2020
Due Sept 28 @ 11:59PM.
For each question you will be marked on programming style as well as correctness.
To see my opinion about what constitutes good programming style
see http://www.engr.mun.ca/~theo/Courses/ds/pub/style.pdf. In short:
• All .java files must be professionally commented; in particular, each file
should contain a comment header that gives your name, student number,
and mun email address. Each subroutine and class should have a comment
at the start of it. I encourage you to use the “javadoc” conventions for
comments.
• Code and comments must be consistently indented; tab stops should be
set every 4 characters.
• Names must be chosen carefully and spelled correctly. (Use names starting
with lower case letters for variables and methods; use names starting with
upper case letters for classes and interfaces.)
• Use subroutines to avoid redundant coding.
• Keep control structures and data structures simple.
All classes must be tested by you prior to being submitted. You are welcome
to share test code with each other.
The assignment is to be done alone. Each file should contain the following
declaration in comments near the top. “This file was prepared by [your name
here]. It was completed by me alone.”. If you obtained help in doing the
assignment, do not include this declaration, but rather an explanation of the
nature of any help that you received in doing the assignment.
Q0. Boolean Expressions
[Learning Objectives: This question requires you to not only implement
an interface in multiple ways but also to write some polymorphic code. In
particular you should find that you have fields whose type is an interface and
to make calls to methods whose exact implementation you do not know. You
will also use an abstract class. This question uses the Abstract Factory pattern
and the composite pattern. end of learning objective]
For this part, we will together create a simple program to print a truth table.
For example, given an input of
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a /\ b \/ ~(a /\ c)
the program will print the following
a b c ((a /\ b) \/ ~ (a /\ c))
false false false true
false false true true
false true false true
false true true true
true false false true
true false true false
true true false true
true true true true
Luckily for you, I’ve written the hardest parts.
Here is how it works: (See class TruthTableMain.)
• Step 0. Two objects work together to create a tree representation of the
input expression. One object is a Parser; it analyzes the input and decides
how the tree should be built. The other class is an ExpressionFactory; it
looks after the details of building the tree.
The above example would be converted to a tree containing 8 nodes. One
node for each occurrence of a variable and one for each of the 4 operators.
Each node will be an object that implements the interface ExpressionNodeI,
which I will provide.
• Step 1. The first line of the output is printed. This involves printing the
tree.
• Step 2. The tree is ‘evaluated’ once for each possible assignment of values
to variables. After each evaluation, the result is printed.
Your job is to create (or complete) the following classes:
• ExpressionFactory: Responsible for creating expression nodes.
• Various nonpublic classes that implement the ExpressionNodeI interface.
• Implement at least one abstract class that has at least 2 subclasses. For
example, you could have one abstract class that is a super class for all
your concrete implementations of ExpressionNodeI, or you could have an
abstract class that is a super class for all classes that represent nodes with
2 children.
Each concrete class that implements the ExpressionNodeI interface must implement
an appropriate constructor and 2 methods:
2
• The first is
public boolean evaluate( Environment env ) ;
This method computes the value of the expression in a given environment.
The environment maps each variable a boolean value (false or true). Each
expression node object will have to evaluate its children (if any) and then
compute and return the appropriate boolean value.
• The second is
public void printTo( PrintWriter p) ;
This method sends a textual representation of the expression to the given
PrintWriter object. ‘And’- and ‘or’-expressions should always be surrounded
by parentheses. (PrintWriter is an interface that supports a print(String)
method.)
Submit the source code for your expressionTree.tree package as a single .zip
file called tree.zip that contains your .java files directly.
Q1. Sets
[Learning Objectives: The first question requires you to implement an
interface and to write some polymorphic code. In particular you should find
that you have to implement methods with parameters whose type is an interface
and to make calls to methods whose exact implementation you do not know.
This assignment also requires you to write at least one iterator class, which will
be a class whose objects are mutable. You will use the Abstract Factory pattern
and the Iterator pattern. end of learning objective]
For this question you will implement an abstract data type representing
finite sets of integers between −2
31 up to (and including) 2
31 − 1.
Implement a public class set.implementation.SetFactory that implements interface
set.SetFactoryI. All other classes should be nonpublic. Classes that implement
the set.SetI interface be immutable (i.e., the objects they describe should
be immutable) and should not be public. There are various data structures you
could use to achieve this goal; you could even use different strategies depending
on the nature of the set, e.g. large and sparse sets could represented one way,
while small, dense sets could be represented another way.
You will need to read about the java.util.Iterator and java.util.Iterable interface.
These are generic interfaces. Conceptually we want java.util.Iterator,
however Java does not allow primitive types as type arguments and so I used
java.util.Iterator. The java.lang.Integer class is a class that described
immutable objects that contain an int value. Luckily conversions between Integer
and int and usually implicit, so you can usually ignore the difference between
Integer and int. For example you can write
for( int i : s ) { System.out.println(i) ; }
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where s is a reference to a SetI object. The iterator object will deliver references
to Integer objects, but they will be implicitly converted to int values before being
assigned to i.
You will need to override the equals method for classes that implement the
SetI interface. Writing equals methods can be tricky. I suggest that you use the
following implementation:
@Override
public boolean equals( Object other ) {
if( other instanceof SetI ) {
SetI otherAsSetI = (SetI) other ;
return otherAsSetI.subset(this) && this.subset( otherAsSetI ) ;
} else {
return false ;
}
}
(It is conventional that, when you override ‘equals’ in Java, you should also
override the ‘hashCode’ method. The reason is that any two objects that are
equal should have the same hash code value, otherwise your class can not be
used as the key type in hash tables. But you may ignore this convention, if you
wish, for this assignment.)
Submit your implementation folder as a .zip file called implemention.zip that
contains your source code directly in it.
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