From 42d5f7545ea6f644d761db207bec4185faadd864 Mon Sep 17 00:00:00 2001
From: Martin Goik <goik@hdm-stuttgart.de>
Date: Mon, 11 Jun 2018 19:34:21 +0200
Subject: [PATCH] @Override example, equals(...) motivation
---
Doc/Sd1/inheritance.xml | 52 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 52 insertions(+)
diff --git a/Doc/Sd1/inheritance.xml b/Doc/Sd1/inheritance.xml
index c63032531..caa241fd6 100644
--- a/Doc/Sd1/inheritance.xml
+++ b/Doc/Sd1/inheritance.xml
@@ -1273,6 +1273,24 @@ Type Rectangle</screen></td>
</informaltable>
</figure>
+ <figure xml:id="sd1_inherit_fig_shapeDefineEqualsExamples">
+ <title>Defining <methodname>equals(...)</methodname>:
+ Expectations</title>
+
+ <programlisting language="java">Rectangle r1 = new Rectangle(1, 2, 5, 4),
+ r2 = new Rectangle(1, 2, 1, 7),
+ r3 = new Rectangle(1, 2, 5, 4);
+
+Circle c = new Circle(-2, 3, 5);
+
+System.out.println(r1.equals("Hello")); // false: Differing classes Rectangle and String.
+System.out.println(r1.equals(r2)); // false: Differing width and height.
+System.out.println(r3.equals(r1)); // true: Two rectangles,
+ // identical (x|y), width and height.
+System.out.println(r1.equals(c)); // false: Differing classes Rectangle and Circle.
+System.out.println(c.equals(c)); // true: Object equal to itself.</programlisting>
+ </figure>
+
<figure xml:id="sd1_inherit_fig_shapeDefineEquals">
<title>Defining <methodname>equals(...)</methodname> of
<classname>Shape</classname> instances</title>
@@ -1402,4 +1420,38 @@ c.equals(r1): false</screen></td>
</informaltable>
</figure>
</section>
+
+ <section xml:id="sd1_inherit_sect_Override">
+ <title>The <classname
+ xlink:href="https://docs.oracle.com/javase/10/docs/api/java/lang/Override.html">@Override</classname>
+ annotation.</title>
+
+ <figure xml:id="sd1_inherit_fig_overrideToString">
+ <title>Overriding Object.toString()</title>
+
+ <programlisting language="java">public class Shape {
+
+ double x, y;
+ ...
+ @Override // Promise: Subsequent method overrides Object.toString();
+ public String toString() {
+ return "(" + x + "|" + y + ")";
+ }
+}</programlisting>
+ </figure>
+
+ <figure xml:id="sd1_inherit_fig_NotOverrideToString">
+ <title>Failure: Not overriding Object.toString()</title>
+
+ <programlisting language="java">public class Shape {
+
+ double x, y;
+ ...
+ @Override <emphasis role="red">// Error: method does not override a method from a supertype</emphasis>
+ public String toString(int value) {
+ return "(" + x + "|" + y + ")";
+ }
+}</programlisting>
+ </figure>
+ </section>
</chapter>
--
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