From 1a6e9bca9e19e02fcb11aec5365e27bc470e3dc2 Mon Sep 17 00:00:00 2001
From: Martin Goik <goik@hdm-stuttgart.de>
Date: Wed, 16 Apr 2014 00:18:20 +0200
Subject: [PATCH] various exercises
---
Sd1/swd1.xml | 271 +++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 265 insertions(+), 6 deletions(-)
diff --git a/Sd1/swd1.xml b/Sd1/swd1.xml
index 297905daa..40efb9d9a 100644
--- a/Sd1/swd1.xml
+++ b/Sd1/swd1.xml
@@ -1766,6 +1766,10 @@ public void writeSvg() {
</glossdef>
</glossentry>
</glosslist>
+
+ <para>For both categories see <xref linkend="bibHorton2011"/>,
+ chapter 5, <quote>Fields in a Class Definition</quote> and
+ <quote>Methods in a Class Definition</quote>.</para>
</glossdef>
</glossentry>
@@ -1793,7 +1797,7 @@ public void writeSvg() {
<programlisting language="java">public class Konto {
...
- private double stand; <emphasis role="bold">// variable stand being shadowed inside setStand(...)</emphasis>
+ private double stand; <emphasis role="bold">// variable "stand" being shadowed inside body of setStand(...)</emphasis>
...
public void setStand(double stand) {
if (stand <= 10000) {
@@ -1807,22 +1811,277 @@ public void writeSvg() {
}</programlisting>
</glossdef>
</glossentry>
+
+ <glossentry>
+ <glossterm>Access restrictions public / private / protected to
+ attributes and methods</glossterm>
+
+ <glossdef>
+ <programlisting>public class Konto {
+
+ private static double // Common interestrate for all accounts being declared
+ guthabenZinssatz = 1.5; // once per class rather than per instance.
+...
+ public void verzinsung() {
+ stand = stand * (1 + guthabenZinssatz / 100);
+ }
+...</programlisting>
+
+ <para>See <xref linkend="bibHorton2011"/>, chapter 5,
+ <quote>CONTROLLING ACCESS TO CLASS MEMBERS</quote>.</para>
+ </glossdef>
+ </glossentry>
+
+ <glossentry>
+ <glossterm>Method overloading</glossterm>
+
+ <glossdef>
+ <para>Example:</para>
+
+ <programlisting>public class Konto {
+
+ public Konto() { // Default constructor without any parameter
+ setStand(0);
+ }
+...
+ public Konto(double stand) { // Non-default constructor defining an account's
+ setStand(stand); // initial value.
+ }
+...
+ public void verzinsung() { // Just one year.
+ stand = stand * (1 + guthabenZinssatz / 100);
+ }
+...
+ public void verzinsung(int jahre) { // Arbitrary number of years.
+ stand = stand * Math.pow((1 + guthabenZinssatz / 100), jahre) ; // raised to the power of jahre, see javadoc comment.
+ }
+...
+}</programlisting>
+
+ <para>See <xref linkend="bibHorton2011"/>, chapter 5, <quote>METHOD
+ OVERLOADING</quote>.</para>
+ </glossdef>
+ </glossentry>
+
+ <glossentry>
+ <glossterm>Use of standard mathematical functions</glossterm>
+
+ <glossdef>
+ <programlisting>Math.pow((1 + guthabenZinssatz / 100), jahre)</programlisting>
+
+ <para>See <xref linkend="bibHorton2011"/>, chapter 2,
+ <quote>MATHEMATICAL FUNCTIONS AND CONSTANTS</quote>.</para>
+ </glossdef>
+ </glossentry>
</glosslist>
</chapter>
- <chapter xml:id="sd1CrabsFinish">
- <title>Lecture 6 - Finishing the crab scenario</title>
+ <chapter xml:id="sd1Variables">
+ <title>Lecture 6 - Variables</title>
<itemizedlist>
<listitem>
- <para>Read chapter 3 of <xref linkend="bibKoelling2010Ger"/>.</para>
+ <para>Read Chapter 2 from <xref linkend="bibHorton2011"/> till
+ <quote>Mathematical Functions and constants</quote>.</para>
</listitem>
<listitem>
- <para>Read Chapter 2 from <xref linkend="bibHorton2011"/> till
- <quote>Mathematical Functions and constants</quote>.</para>
+ <para>Read chapter 3 of <xref linkend="bibKoelling2010Ger"/>.</para>
</listitem>
</itemizedlist>
+
+ <section xml:id="sd1VariableExercises">
+ <title>Exercises</title>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1VariableComplexExpression">
+ <title>Programmers favourite expression</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider the following code fragment:</para>
+
+ <programlisting> int a = 6,
+ b = 7,
+ c = -3,
+ result = 0;
+
+ result += ++a - b++ + --c;</programlisting>
+
+ <para>Rewrite this code by decomposing the last line into
+ several lines to make the code easier to understand. Hint: After
+ execution all variable shall have identical values.</para>
+ </question>
+
+ <answer>
+ <para>Incrementing <code>a</code> and decrementing
+ <code>c</code> happens prior to adding their values to the
+ variable <code>result</code>. The increment operation of
+ <code>b</code> in contrast happens after being being subtracted
+ from result. This determines a possible decomposition:</para>
+
+ <programlisting> int a = 6,
+ b = 7,
+ c = -3,
+ result = 0;
+ ++a;
+ --c;
+ result += a - b + c;
+ b++;</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sd1QandaIntOverflow">
+ <title>Integer value considerations.</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Consider the following piece of code:</para>
+
+ <programlisting>int a = ..., b = ...;
+...// some calculations being omitted
+int sum = a + b;</programlisting>
+
+ <para>Which problem may arise here? May you supply a
+ solution?</para>
+ </question>
+
+ <answer>
+ <para>The sum of a and b may either exceed
+ <code>java.lang.Integer.MAX_VALUE</code> or in turn may be less
+ than <code>java.lang.Integer.MIN_VALUE</code>. To avoid this
+ type of overflow error our variable <code>sum</code> may be
+ declared as long:</para>
+
+ <programlisting>int a = ..., b = ...;
+...// some calculations being omitted
+long sum = a + b;</programlisting>
+
+ <para>Unfortunately this does not (yet) help at all: Since both
+ operands <code>a</code> and <code>b</code> are of type
+ <code>int</code> the expression <code>a + b</code> is also of
+ type int. The only way to solve this problem is by casting at
+ least one operand to <code>long</code>:</para>
+
+ <programlisting>int a = ..., b = ...;
+...// some calculations being omitted
+long sum = (long)a + b;</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+
+ <qandaset defaultlabel="qanda" xml:id="sde1QandaFraction">
+ <title>A class representing fractions</title>
+
+ <qandadiv>
+ <qandaentry>
+ <question>
+ <para>Implement a class representing fractions. The desired
+ interface is being described in the subfolder
+ Fraction/index.html below the <link
+ xlink:href="https://cloud.mi.hdm-stuttgart.de/owncloud/public.php?service=files&t=df9f296af3298f96361a15a679390e59">set
+ of additional lecture resources</link>. The following code
+ snippet illustrates the possible usage:</para>
+
+ <programlisting> Fraction twoThird = new Fraction(2, 3), // Construct a fraction object (2/3)
+ threeSeven = new Fraction(3, 7); // Construct a fraction object (3/7)
+
+ Fraction sum = twoThird.add(threeSeven), // (2/3) + (3/7)
+ product = twoThird.mult(threeSeven); // (2/3) * (3/7)
+
+ System.out.println("Sum:" + sum.getValue()); // Expected to be (23/21)
+ System.out.println("Product:" + product.getValue()); // Expected to be (2/7)</programlisting>
+ </question>
+
+ <answer>
+ <programlisting>package math;
+
+public class Fraction {
+
+ long numerator,denominator;
+
+ /**
+ * @param numerator
+ * @param denominator
+ */
+ public Fraction(long numerator, long denominator) {
+ setNumerator(numerator);
+ setDenominator(denominator);
+ }
+ /**
+ * @return
+ * The fraction's decimal value e.g. 1/3 = 0.3333...
+ */
+ public double getValue(){
+ return (double) numerator / denominator;
+ }
+ /**
+ * @return
+ * The fraction's numerator
+ */
+ public long getNumerator() {
+ return numerator;
+ }
+ /**
+ * Set the fraction's numerator.
+ * @param numerator
+ */
+ public void setNumerator(long numerator) {
+ this.numerator = numerator;
+ }
+ /**
+ * @return
+ * The fraction's denominator value
+ */
+ public long getDenominator() {
+ return denominator;
+ }
+ /**
+ * Set the fraction's denominator
+ * @param denominator
+ */
+ public void setDenominator(long denominator) {
+ this.denominator = denominator;
+ }
+
+ /**
+ * Add a second fraction to the current instance.
+ *
+ * @param f
+ *
+ * @return
+ * The sum of the current instance and f.
+ */
+ public Fraction add(Fraction f) {
+ return new Fraction( numerator * f.denominator + denominator * f.numerator,
+ denominator * f.denominator);
+ }
+ /**
+ * Multiply a second fraction by this instance
+ * @param f
+ * @return
+ * The result of multiplying the current instance by f.
+ */
+ public Fraction mult(Fraction f) {
+ return new Fraction(numerator * f.numerator,
+ denominator * f.denominator);
+ }
+}</programlisting>
+ </answer>
+ </qandaentry>
+ </qandadiv>
+ </qandaset>
+ </section>
+ </chapter>
+
+ <chapter xml:id="sd1L7">
+ <title>Lecture 7</title>
+
+ <para/>
</chapter>
<chapter xml:id="ideas">
--
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