Merge pull request #175 from RunestoneInteractive/ternary

Improvements to chapter 4

Author: pearcej

source/ch4_conditionals.ptx

@@ -162,17 +162,18 @@ public class ElseIf {
         <title>Using the <c>switch</c> Statement</title>
 
         <p>
-Java also supports a <c>switch</c> statement that acts something like the <c>elif</c> statement of Python under certain conditions. To write the grade program using a <c>switch</c> statement we would use the following:
-</p>
+Java also supports a <c>switch</c> statement that acts something like the <c>elif</c> or Python <c>match</c> statement under certain conditions. To write the grade program using a <c>switch</c> statement we would use the following:
+</p
 
         <note>
             <p>
-                Depending on your knowledge and experience with Python you may be questioning why we are not using the <c>match</c> statement in our Python examples. The answer is that this book currently runs its active code examples using Python 3.7, which does not support the <c>match</c> statement which was introduced in Python 3.10. Below is an example of the <c>match</c> statement similar to our grade method.
+                The <c>match - case</c> statement was introduced in Python 3.10, so doesn't run in earlier version of Python. Here is an example using Python's <c>match - case</c> structure.
             </p>
                     <program xml:id="python-match" language="python">
             <title>Match Case Example</title>
             <code>
                 grade = 85
+                # Convert grade to a scale of 0-10 using integer division
                 tempgrade = grade // 10
                 def grading(tempgrade):
                     match grade:
@@ -192,7 +193,7 @@ Java also supports a <c>switch</c> statement that acts something like the <c>eli
         </note>
 
         <p><idx><c>switch</c></idx>
-            The <c>switch</c> statement in Java provides a clean and efficient alternative to chaining multiple <c>if-else</c> conditions, especially when comparing a single variable against several constant values. It supports a variety of data types, including primitive types (<c>byte</c>, <c>short</c>, <c>char</c>, <c>int</c>), their wrapper classes, <c>enumerations</c>, and <c>String</c> (introduced in Java 7). Each <c>case</c> within a <c>switch</c> must be defined using a constant expression, and duplicate <c>case</c> values are not permitted. By default, control flow "<c>falls through</c>" from one <c>case</c> to the next unless a <c>break</c>, <c>return</c>, or <c>throw</c> statement is used to terminate execution. 
+            The <c>switch</c> statement in Java provides an alternative to chaining multiple <c>if-else</c> conditions,  when comparing a single variable against several constant values. It supports a variety of data types, including primitive types (<c>byte</c>, <c>short</c>, <c>char</c>, <c>int</c>), their wrapper classes, <c>enumerations</c>, and <c>String</c> (introduced in Java 7). Each <c>case</c> within a <c>switch</c> must be defined using a constant expression, and duplicate <c>case</c> values are not permitted. By default, control flow "<c>falls through</c>" from one <c>case</c> to the next unless a <c>break</c>, <c>return</c>, or <c>throw</c> statement is used to terminate execution. 
         </p>
 
         <p>
@@ -204,8 +205,9 @@ Java also supports a <c>switch</c> statement that acts something like the <c>eli
         <program xml:id="java-switch-up" interactive="activecode" language="java">
             <code>
             public class SwitchUp {
-                public static void main(String args[]) {
+              public static void main(String args[]) {
                 int grade = 85;
+                // Convert grade to a scale of 0-10 using integer division
                 int tempgrade = grade / 10;
                 switch(tempgrade) {
                 case 10:
@@ -224,14 +226,16 @@ Java also supports a <c>switch</c> statement that acts something like the <c>eli
                 default:
                     System.out.println('F');
                 }
-            }
+              }
             }
             </code> <tests> </tests>
         </program>
 
         <p>
 The <c>switch</c> statement is not used very often, and we recommend you do not use it. First, it is not as powerful as the <c>else if</c> model because the switch variable can only be compared for equality with an integer or enumerated constant. Second, it is very easy to forget to put in the <c>break</c> statement, so it is more error-prone. If the break statement is left out then then the next alternative will be automatically executed. For example, if the grade was 95 and the <c>break</c> was omitted from the <c>case 9:</c> alternative then the program would print(out both A and B.)
         </p>
+        <p>
+            Finally, the <c>switch</c> statement does not support relational expressions such as greater than or less than. So you cannot use it to completely replace the <c>elif</c>. Even with the new features of Java 14+ the <c>switch</c> statement is still limited to constant comparisons using equality.</p>
     </section>
 
     <section xml:id="exception-handling">
@@ -385,17 +389,15 @@ The <c>switch</c> statement is not used very often, and we recommend you do not
 
     </section>
 
-    <section xml:id="boolean-operators">
-        <title>Boolean Operators</title>
+    <section xml:id="ternary-operator">
+        <title>The Ternary Operator</title>
 
         <p><idx>Boolean operators</idx> <idx>simple comparisons</idx> <idx>compound Boolean expressions</idx>
 The conditionals used in the if statement can be <term>Boolean variables</term>, <term>simple comparisons</term>, and <term>compound Boolean expressions</term>.
         </p>
 
 <p><idx>ternary operator</idx>
-Java also supports the <c>boolean</c> expression using the ternary operator 
-<c>condition ? trueValue : falseValue</c>. This operator tests a condition as part 
-of an assignment statement. The following table summarizes how this works:
+Java also provides the ternary operator <c>condition ? valueIfTrue : valueIfFalse</c>, which lets you use a <c>boolean</c> test directly inside an assignment. If the condition is true, the first value is chosen; otherwise, the second value is used. The table below summarizes how it works:
 </p>
 
 <table>
@@ -437,27 +439,35 @@ of an assignment statement. The following table summarizes how this works:
 </table>
 
 <p>
-Using this operator can make code shorter and more readable in cases where a simple conditional assignment is needed.
+Using this operator can make code shorter and more readable in cases where a simple conditional assignment is needed. See the following as an example where we see the same logic implemented in two different ways.
 </p>
-        <program xml:id="java-ternary" interactive ="activecode" language ="java">
+        <program xml:id="java-ternary" interactive="activecode" language ="java">
             <code>
-                class Main {
-                        public static void main(String[] args) {
-                        int a = 4;
-                        int x = 2;
-
-                        // Using the ternary operator
-                        a = (a % 2 == 0) ? a * a : 3 * x - 1;
+public class Ternary {
+    public static void main(String[] args) {
+        int a = 4;
+        int x = 2;
+        int outp;
+
+        // ternary:
+        outp = (a % 2 == 0) ? (a * a) : (3 * x - 1);
+        System.out.println("ternary result: " + outp);
+
+        // Equivalent using if/else
+        if (a % 2 == 0) {
+            outp = a * a;
+        } else {
+            outp = 3 * x - 1;
+        }
 
-                        System.out.println("Result: " + a);
-                    }
-                }
-                  
+        System.out.println("if/else result: " + outp);
+    }
+}
             </code>
         </program>
 
         <p>
-            In this example we are using this ternary operator to assign a value to <c>a</c> based on whether <c>a</c> is even or odd. If <c>a</c> is even, it will be squared; if odd, it will be instead be calculated as <c>3 * x - 1</c>. This is a concise way to write conditional assignments in Java. However, it should be used reasonably, as it can make code less readable if overused or used in complex expressions.
+            In this example we are using this ternary operator to assign a value to <c>a</c> based on whether <c>a</c> is even or odd. If <c>a</c> is even, it will be squared; if odd, it will be instead be calculated as <c>3 * x - 1</c>. This is a concise way to write conditional assignments in Java. However, you might want to use it sparingly, as it can make code less readable if overused or used with complex expressions.
         </p>
 
 
@@ -473,7 +483,7 @@ Using this operator can make code shorter and more readable in cases where a sim
             </li>
             <li>
                 <p>
-                    Java's <c>switch</c> statement is similar to Python's <c>match</c> statement, but it only supports equality checks against constant values and does not evaluate relational expressions like greater than or less than.
+                    Java's <c>switch</c> statement is similar to Python's <c>match</c> statement, but it only supports equality checks against constant values and does not evaluate relational expressions like greater than or less than. 
                 </p>
 
             </li>