diff --git a/ws/eclipse/Sda1PreExam/Exercises/OO/ex1.xhtml b/ws/eclipse/Sda1PreExam/Exercises/OO/ex1.xhtml
index 51e124316de7ab81e6ef0e70d51e2868b7ba6ef5..0e8029bb34f0f81f840dc6ab4491769d3c185ae3 100644
--- a/ws/eclipse/Sda1PreExam/Exercises/OO/ex1.xhtml
+++ b/ws/eclipse/Sda1PreExam/Exercises/OO/ex1.xhtml
@@ -6,88 +6,92 @@
</head>
<body><h1>A party statistics application</h1><p>Implement the following
- interface:</p><pre><code>package party1;
+ interface <b>using the eclipse IDE</b>:</p>
+<pre><code>package party1;</code></pre>
+<pre><code></code></pre>
+<pre><code>/**</code></pre>
+<pre><code> * Provide statistical information regarding a party. We distinguish</code></pre>
+<pre><code> * between the numbers of guests and the number of organizers.</code></pre>
+<pre><code> * The whole party will cost a certain amount of money being defined </code></pre>
+<pre><code> * by calling {@link #setExpenses(float)}.</code></pre>
+<pre><code> * </code></pre>
+<pre><code> * These expenses will be paid by the organizers, the latter being set</code></pre>
+<pre><code> * by calling {@link #setNumberOfOrganizers(int)}. Each organizer will have to</code></pre>
+<pre><code> * pay his corresponding share.</code></pre>
+<pre><code> *</code></pre>
+<pre><code> */</code></pre>
+<pre><code>public interface PartyStatistics {</code></pre>
+<pre><code> </code></pre>
+<pre><code> /**</code></pre>
+<pre><code> * @param numGuests The number of guests attending the party,</code></pre>
+<pre><code> * default value is zero.</code></pre>
+<pre><code> */</code></pre>
+<pre><code> public void setNumberOfGuests(int numGuests);</code></pre>
+<pre><code> </code></pre>
+<pre><code> /**</code></pre>
+<pre><code> * @param numOrganizers The number of persons organizing the party,</code></pre>
+<pre><code> * default value is zero.</code></pre>
+<pre><code> */</code></pre>
+<pre><code> public void setNumberOfOrganizers(int numOrganizers);</code></pre>
+<pre><code> </code></pre>
+<pre><code> /**</code></pre>
+<pre><code> * </code></pre>
+<pre><code> * @param expenses The sum of all costs the party has caused.</code></pre>
+<pre><code> * Default value is zero (0f)</code></pre>
+<pre><code> */</code></pre>
+<pre><code> public void setExpenses(float expenses);</code></pre>
+<pre><code> </code></pre>
+<pre><code> /**</code></pre>
+<pre><code> * We assume that all party participants shake hands with each</code></pre>
+<pre><code> * other at arrival. Example: Having one organizer and three guests</code></pre>
+<pre><code> * results in six handshakes.</code></pre>
+<pre><code> * </code></pre>
+<pre><code> * @return The total number of handshakes among all guests and organizers.</code></pre>
+<pre><code> */</code></pre>
+<pre><code> public int getNumberOfHandshakes();</code></pre>
+<pre><code> </code></pre>
+<pre><code> /**</code></pre>
+<pre><code> * Expenses will be shared by all organizers.</code></pre>
+<pre><code> * @return Each organizer's share according to {@link #setExpenses(float)} and </code></pre>
+<pre><code> * {@link #setNumberOfOrganizers(int)}</code></pre>
+<pre><code> */</code></pre>
+<pre><code> public float getAverageExpenses();</code></pre>
+<pre><code>}</code></pre>
-
-/**
- * Provide statistical information regarding a party. We distinguish
- * between the numbers of guests and the number of organizers.
- * The whole party will cost a certain amount of money being defined
- * by calling {@link #setExpenses(float)}.
- *
- * These expenses will be paid by the organizers, the latter being set
- * by calling {@link #setNumberOfOrganizers(int)}. Each organizer will have to
- * pay his corresponding share.
- *
- */
-public interface PartyStatistics {
-
- /**
- * @param numGuests The number of guests attending the party,
- * default value is zero.
- */
- public void setNumberOfGuests(int numGuests);
-
- /**
- * @param numOrganizers The number of persons organizing the party,
- * default value is zero.
- */
- public void setNumberOfOrganizers(int numOrganizers);
-
- /**
- *
- * @param expenses The sum of all costs the party has caused.
- * Default value is zero (0f)
- */
- public void setExpenses(float expenses);
-
- /**
- * We assume that all party participants shake hands with each
- * other at arrival. Example: Having one organizer and three guests
- * results in six handshakes.
- *
- * @return The total number of handshakes among all guests and organizers.
- */
- public int getNumberOfHandshakes();
-
- /**
- * Expenses will be shared by all organizers.
- * @return Each organizer's share according to {@link #setExpenses(float)} and
- * {@link #setNumberOfOrganizers(int)}
- */
- public float getAverageExpenses();
-}</code></pre><h1>Solution</h1><p>An implementing class needs to keep track
+<h1>Solution</h1><p>An implementing class needs to keep track
about state being changed by invocations of <code>setExpenses(float
expenses)</code>, <code>setNumberOfGuests(int numGuests)</code> and
<code>setNumberOfOrganizers(int numOrganizers)</code>. Thus we need three
corresponding instance variables <code>expenses</code>,
- <code>numGuests</code> and <code>numOrganizers</code>:</p><pre><code>package party1;
-
-public class PartyStatisticsImpl implements PartyStatistics {
-
- @Override
- public void setNumberOfGuests(int numGuests) { this.numGuests = numGuests;}
-
- @Override
- public void setNumberOfOrganizers(int numOrganizers) { this.numOrganizers = numOrganizers;}
-
- @Override
- public void setExpenses(float expenses) { this.expenses = expenses;}
-
- @Override
- public float getAverageExpenses() {
- return expenses / numOrganizers;
- }
- @Override
- public int getNumberOfHandshakes() {
- final int totalPersonsNum = numGuests + numOrganizers;
- return totalPersonsNum * (totalPersonsNum - 1) / 2;
- }
-
- int numGuests = 0;
- int numOrganizers = 0;
- float expenses = 0f;
-}</code></pre><p>The three internal values must be initialized to zero in
+ <code>numGuests</code> and <code>numOrganizers</code>:</p>
+<pre><code>package party1;</code></pre>
+<pre><code></code></pre>
+<pre><code>public class PartyStatisticsImpl implements PartyStatistics {</code></pre>
+<pre><code> </code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> public void setNumberOfGuests(int numGuests) { this.numGuests = numGuests;}</code></pre>
+<pre><code></code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> public void setNumberOfOrganizers(int numOrganizers) { this.numOrganizers = numOrganizers;}</code></pre>
+<pre><code></code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> public void setExpenses(float expenses) { this.expenses = expenses;}</code></pre>
+<pre><code></code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> public float getAverageExpenses() {</code></pre>
+<pre><code> return expenses / numOrganizers;</code></pre>
+<pre><code> }</code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> public int getNumberOfHandshakes() {</code></pre>
+<pre><code> final int totalPersonsNum = numGuests + numOrganizers;</code></pre>
+<pre><code> return totalPersonsNum * (totalPersonsNum - 1) / 2;</code></pre>
+<pre><code> }</code></pre>
+<pre><code> </code></pre>
+<pre><code> int numGuests = 0;</code></pre>
+<pre><code> int numOrganizers = 0;</code></pre>
+<pre><code> float expenses = 0f;</code></pre>
+<pre><code>}</code></pre>
+<p>The three internal values must be initialized to zero in
accordance with their defaults as being described in the methods'
documentation of the interface <code>PartyStatistics</code>.</p></body>
</html>
diff --git a/ws/eclipse/Sda1PreExam/Exercises/OO/ex2.xhtml b/ws/eclipse/Sda1PreExam/Exercises/OO/ex2.xhtml
index 9420ead8680dcba7c4effa5fbcab337d2c5bea34..1a7105f27af8f449cff5d5eecf426b927088bc6e 100644
--- a/ws/eclipse/Sda1PreExam/Exercises/OO/ex2.xhtml
+++ b/ws/eclipse/Sda1PreExam/Exercises/OO/ex2.xhtml
@@ -5,24 +5,31 @@
<title></title>
</head>
- <body><h1>The <code>Override</code> annotation</h1><p>In the suggested
- solution of the previous exercise you found the
- <code>java.lang.Override</code> annotation:</p><pre><code>...
+ <body>
+ <!-- Exercise 1 -->
-public class PartyStatisticsImpl implements PartyStatistics {
-
- <b>@Override</b>
- public void setNumberOfGuests(int numGuests) { this.numGuests = numGuests;}
+ <h1>The <code>Override</code> annotation</h1>
+ <p>In the suggested
+ solution of the previous exercise you will find the
+ <code>java.lang.Override</code> annotation:</p>
+<pre><code>...</code></pre>
+<pre><code>public class PartyStatisticsImpl implements PartyStatistics { </code></pre>
+<pre><code> <b>@Override</b></code></pre>
+<pre><code> public void setNumberOfGuests(int numGuests) { ...}</code></pre>
+<pre><code>...</code></pre>
-...</code></pre><p>Answer the following three questions:</p><ol>
+ <p>Answer the following three questions with respect to <code>@override</code>:</p><ol>
<li>Explain its precise meaning in the current context.</li>
- <li>Do you know a different Java meaning of <code>Override</code> in
- context of a related problem?</li>
+ <li>Do you know a different Java meaning of <code>@Override</code> in a
+ similar but yet different context?</li>
<li>What happens to the way the code executes if the
- <code>Override</code> annotations are being erased?</li>
- </ol><h1>Solution</h1><ol>
+ <code>@Override</code> annotations are being omitted? Whats the catch of
+ using <code>@Override</code>?</li>
+ </ol>
+
+<h1>Solution</h1><ol>
<li>The method <code>void setNumberOfGuests(int numGuests)</code> in
class <code>PartyStatisticsImpl</code> implements a method <code>void
setNumberOfGuests(int numGuests)</code> from the interface
@@ -31,80 +38,111 @@ public class PartyStatisticsImpl implements PartyStatistics {
<li><p>The <code>Override</code> annotation may indicate that a method
in a derived class overrides a corresponding method in one of its parent
classes (in a given inheritance hierarchy). Consider the following
- example:</p><pre><code><b>File A.java:</b>
-
-public class A {
- void myDoNothingMethod(){}
-}
-----------------------------------
-<b>File B.java</b>:
-
-public class B extends A {
- // More code to be added later
-}
------------------------------------
-<b>File C.java</b>;
+ example:</p>
+<pre><code><b>File A.java:</b></code></pre>
+<pre><code></code></pre>
+<pre><code>public class A {</code></pre>
+<pre><code> void myDoNothingMethod(){}</code></pre>
+<pre><code>}</code></pre>
+<pre><code>----------------------------------</code></pre>
+<pre><code><b>File B.java:</b></code></pre>
+<pre><code></code></pre>
+<pre><code>public class B extends A {</code></pre>
+<pre><code> // More code to be added later</code></pre>
+<pre><code>}</code></pre>
+<pre><code>-----------------------------------</code></pre>
+<pre><code><b>File C.java</b>;</code></pre>
+<pre><code></code></pre>
+<pre><code>public class C extends B {</code></pre>
+<pre><code></code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> void myDoNothingMethod() {}</code></pre>
+<pre><code>}</code></pre>
+</li>
-public class C extends B {
+ <li><p>Nothing. But accidentally changing the method's name or signature
+ yields a compiler error. Consider the following example:</p>
- @Override
- void myDoNothingMethod() {}
-}</code></pre></li>
+<pre><code>...</code></pre>
+<pre><code></code></pre>
+<pre><code>public class PartyStatisticsImpl implements PartyStatistics {</code></pre>
+<pre><code> </code></pre>
+<pre><code> <b>@Override</b></code></pre>
+<pre><code> public void setNumberOfGuest(int numGuests) { this.numGuests = numGuests;}</code></pre>
+<pre><code></code></pre>
+<pre><code>...</code></pre>
- <li><p>Nothing. But accidentally changing the method's signature yields
- a compiler error. Consider the following example:</p><pre><code>...
-
-public class PartyStatisticsImpl implements PartyStatistics {
-
- <b>@Override</b>
- public void setNumberOfGuest(int numGuests) { this.numGuests = numGuests;}
-
-...</code></pre><p>Do you see the typo? The <q>s</q> is missing at the end of
+<p>Do you see the typo? The "s" is missing at the end of
<code>setNumberOfGuest</code>. Thanks to the <code>Override</code>
annotation this mistake gets flagged by a compile time error <q>The
method setNumberOfGuest(int) of type PartyStatisticsImpl must override
- or implement a supertype method</q>.</p></li>
- </ol><h1>Handling missing organizers</h1><p>Our (Your??) current
- implementation contains a problem. The method float getAverageExpenses()
- assumes a non-zero number as being stated in its documentation. Violating
+ or implement a supertype method</q>. Similar using a different parameter
+ type e.g. <code>String</code> in favour of <code>int</code> will be
+ flagged as an error, too.</p></li>
+ </ol>
+
+<h1>Handling missing organizers</h1>
+<p>Our (Your??) current
+ implementation contains a problem. The method <code>float getAverageExpenses()</code>
+ assumes a non-zero number of organizers to share expenses as being stated in its documentation. Violating
this precondition yields a division by zero and thus an unchecked runtime
- exception due to:</p><pre><code>@Override
-public float getAverageExpenses() {
- return expenses / <b>numOrganizers</b>;
-}</code></pre><p>We want to have a checked exception instead. Modify both the
+ exception due to:</p>
+<pre><code></code></pre>
+<pre><code>@Override</code></pre>
+<pre><code>public float getAverageExpenses() {</code></pre>
+<pre><code> return expenses / <b>numOrganizers</b>;</code></pre>
+<pre><code>}</code></pre>
+<p>We want to have a checked exception instead. Modify both the
interface and your implementation accordingly by introducing a
- <b>suitable</b> exception class.</p><h1>Solution</h1><p>We add an exception
- class related to arithmetic errors:</p><pre><code>/**
- * According to {@link PartyStatistics#getAverageExpenses()} a party's
- * costs will be shared by the organizers and thus divided by their respective
- * number. If the number of organizers is zero this exception
- * will be thrown on invocation of {@link PartyStatistics#getAverageExpenses()}.
- *
- */
-public class <b>NoOrganizerException extends ArithmeticException</b> {
- @Override
- public String getMessage() {
- return "No organizer has been defined. How shall I share costs?";
- }
-}</code></pre><p>We have to modify our interface:</p><pre><code>public interface PartyStatistics {
-
- ...
- /**
- * Expenses will be shared by all organizers.
- * @return Each organizer's share according to {@link #setExpenses(float)} and
- * {@link #setNumberOfOrganizers(int)}
- * @throws NoOrganizerException in case the number of organizers is zero
- */
- public float getAverageExpenses() <b>throws NoOrganizerException</b>;
-
-}</code></pre><p>Our implementation now reads:</p><pre><code>...
-@Override
-public float getAverageExpenses() throws NoOrganizerException {
- if (0 < numOrganizers) {
- return expenses / numOrganizers;
- } else {
- throw new NoOrganizerException();
- }
-}
-...</code></pre></body>
+ <b>suitable</b> exception class.</p>
+
+<!-- Exercise 2 -->
+
+<h1>Solution</h1>
+
+<p>We add an exception
+ class related to arithmetic errors:</p>
+<pre><code></code></pre>
+<pre><code>/**</code></pre>
+<pre><code> * According to {@link PartyStatistics#getAverageExpenses()} a party's</code></pre>
+<pre><code> * costs will be shared by the organizers and thus divided by their respective</code></pre>
+<pre><code> * number. If the number of organizers is zero this exception</code></pre>
+<pre><code> * will be thrown on invocation of {@link PartyStatistics#getAverageExpenses()}.</code></pre>
+<pre><code> *</code></pre>
+<pre><code> */</code></pre>
+<pre><code>public class <b>NoOrganizerException extends ArithmeticException</b> {</code></pre>
+<pre><code> @Override</code></pre>
+<pre><code> public String getMessage() {</code></pre>
+<pre><code> return "No organizer has been defined. How shall I share costs?";</code></pre>
+<pre><code> }</code></pre>
+<pre><code>}</code></pre>
+
+<p>We have to modify our interface accordingly:</p>
+
+<pre><code></code></pre>
+<pre><code>public interface PartyStatistics {</code></pre>
+<pre><code> </code></pre>
+<pre><code> ... </code></pre>
+<pre><code> /**</code></pre>
+<pre><code> * Expenses will be shared by all organizers.</code></pre>
+<pre><code> * @return Each organizer's share according to {@link #setExpenses(float)} and </code></pre>
+<pre><code> * {@link #setNumberOfOrganizers(int)}</code></pre>
+<pre><code> * <b>@throws NoOrganizerException in case the number of organizers is zero</b></code></pre>
+<pre><code> */</code></pre>
+<pre><code> public float getAverageExpenses() <b>throws NoOrganizerException</b>;</code></pre>
+<pre><code> </code></pre>
+<pre><code>}</code></pre>
+
+<p>Our implementation now reads:</p>
+<pre><code>...</code></pre>
+<pre><code>@Override</code></pre>
+<pre><code>public float getAverageExpenses() <b>throws NoOrganizerException</b> {</code></pre>
+<pre><code> if (0 < numOrganizers) {</code></pre>
+<pre><code> return expenses / numOrganizers;</code></pre>
+<pre><code> } else {</code></pre>
+<pre><code> <b>throw new NoOrganizerException();</b></code></pre>
+<pre><code> }</code></pre>
+<pre><code>}</code></pre>
+<pre><code>...</code></pre>
+</body>
</html>