@Override example, equals(...) motivation

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>