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Issue 299 fixed: Added listing tags to 6.3 #307

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Merged
pearcej merged 5 commits into from
Aug 3, 2026
+17 −12
Merged

Issue 299 fixed: Added listing tags to 6.3 #307

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b859e71
added listing tags
habibasorour Jul 31, 2026
4359d36
made the xml:id more defined
habibasorour Jul 31, 2026
e0796f8
made half programs that won't run on its own in a different format
habibasorour Jul 31, 2026
d83e30d
add listing to txt
habibasorour Jul 31, 2026
ae6b7ae
add listing to txt
habibasorour Jul 31, 2026
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29 changes: 17 additions & 12 deletions source/ch6_definingclasses.ptx
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Original file line number Diff line number Diff line change
Expand Up @@ -277,11 +277,11 @@ public Fraction(Integer num, Integer den) {
However, if you reassign the parameter to a completely new object inside the method (e.g., <c>otherFrac = new Fraction(0,1);</c>), it would <em>not</em> affect the original variable outside the method, because you are only changing the local copy of the reference.
</p>
<p>
Let&#x2019;s begin by implementing addition in Java:
<xref ref="java-fraction-class-addition-initial" text="type-global"/> shows the first part of the Fraction class definition.
</p>


<program xml:id="java-fraction-class-addition" language="java">
<listing xml:id="java-fraction-class-addition-initial">
<program>
<code>
public Fraction add(Fraction otherFrac) {
Integer newNum = otherFrac.getDenominator() * this.numerator +
Expand All @@ -292,6 +292,7 @@ public Fraction add(Fraction otherFrac) {
}
</code>
</program>
</listing>

<p>
First you will notice that the <c>add</c> method is declared as <c>public Fraction</c> The <c>public</c> part means that any other method may call the <c>add</c> method.
Expand All @@ -301,11 +302,11 @@ public Fraction add(Fraction otherFrac) {
<p>
Second, you will notice that the method makes use of the <c>this</c> variable.
In this method, <c>this</c> is not necessary, because there is no ambiguity about the <c>numerator</c> and <c>denominator</c> variables.
So the following version of the code is equivalent:
<xref ref="java-fraction-class-addition-equivalent" text="type-global"/> is an equivalent version of <xref ref="java-fraction-class-addition-initial" text="type-global"/>.
</p>


<program xml:id="java-fraction-class-addition2" language="java">
<listing xml:id="java-fraction-class-addition-equivalent">
<program>
<code>
public Fraction add(Fraction otherFrac) {
Integer newNum = otherFrac.getDenominator() * numerator +
Expand All @@ -316,6 +317,7 @@ public Fraction add(Fraction otherFrac) {
}
</code>
</program>
</listing>

<p>
The addition takes place by multiplying each numerator by the opposite denominator before adding.
Expand Down Expand Up @@ -362,11 +364,11 @@ public Fraction add(Fraction otherFrac) {
To solve the problem of adding an <c>Integer</c> and a <c>Fraction</c> in Java we will overload both the constructor and the <c>add</c> method.
We will overload the constructor so that if it only receives a single <c>Integer</c> it will convert the <c>Integer</c> into a <c>Fraction</c>.
We will also overload the <c>add</c> method so that if it receives an <c>Integer</c> as a parameter it will first construct a <c>Fraction</c> from that integer and then add the two <c>Fractions</c> together.
The new methods that accomplish this task are as follows:
<xref ref="java-method-overloading" text="type-global"/> shows the new methods that accomplish this task.
</p>


<program xml:id="java-method-overloading" language="java">
<listing xml:id="java-method-overloading">
<program>
<code>
public Fraction(Integer num) {
this.numerator = num;
Expand All @@ -377,6 +379,7 @@ public Fraction add(Integer other) {
}
</code>
</program>
</listing>

<p>
Notice that the overloading approach can provide us with a certain elegance to our code.
Expand All @@ -385,12 +388,12 @@ public Fraction add(Integer other) {
</p>

<p>
Our full <c>Fraction</c> class to this point would look like the following.
Our full <c>Fraction</c> class to this point would look <xref ref="java-full-fraction-class" text="type-global"/>.
You should compile and run the program to see what happens.
</p>


<program xml:id="java-full-fraction-class" interactive="activecode" language="java">
<listing xml:id="java-full-fraction-class">
<program interactive="activecode" language="java">
<code>
public class Fraction {
private Integer numerator;
Expand Down Expand Up @@ -434,6 +437,8 @@ public class Fraction {
}
</code> <tests> </tests>
</program>
</listing>

</subsection>
</section>

Expand Down