review comments

Java8/README.md

@@ -223,9 +223,10 @@ Here's an overview of what's currently included in these examples:
          ReentrantReadWriteLock, synchronized statements, and
          VarHandle.
 
-. ex40 - This program demonstrates how to use modern Java features to
-         build a cosine vector Map from a CSV file containing the
-         cosine values for movies.
+. ex40 - This program demonstrates how to use modern Java features
+         (including lambda expressions, method references, and
+         parallel streams) to build a cosine vector Map from a CSV
+         file containing the cosine values for movies.
 
 . ex41 - This program shows the difference between using traditional
          Java 7 features to replace substrings vs. using modern Java

Java8/ex10/.run/ex10.run.xml

@@ -1,6 +1,6 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="ex10" type="Application" factoryName="Application">
-    <option name="ALTERNATIVE_JRE_PATH" value="openjdk-18" />
+    <option name="ALTERNATIVE_JRE_PATH" value="$USER_HOME$/Library/Java/JavaVirtualMachines/corretto-11.0.14.1/Contents/Home" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="true" />
     <option name="MAIN_CLASS_NAME" value="ex10" />
     <module name="Example 10" />

Java8/ex10/src/ex10.java

@@ -31,6 +31,7 @@ static public void main(String[] argv) {
         Map<String, Integer> stooges = makeMap();
 
         System.out.println(stooges);
+
         // This lambda expression removes entries with IQ less than or
         // equal to 100.
         stooges.entrySet().removeIf(entry -> entry.getValue() <= 100);
@@ -50,7 +51,6 @@ static public void main(String[] argv) {
         // This lambda expression removes entries with IQ less than or
         // equal to 100 with the name "curly".
         stooges.entrySet().removeIf(iq.and(curly));
-
         System.out.println(stooges);
     }
 }

Java8/ex40/src/main/java/ex40.java

@@ -12,7 +12,8 @@
 import static java.util.stream.Collectors.toMap;
 
 /**
- * This program demonstrates how to use modern Java features to build
+ * This program demonstrates how to use modern Java features (including
+ * lambda expressions, method references, and parallel streams) to build
  * a cosine vector {@link Map} from a CSV file containing the cosine
  * values for movies.
  */
@@ -59,10 +60,13 @@ public static Map<String, List<Double>> vectorMap(final String dataset) {
      */
     private static Map<String, List<Double>> loadCSVFile(String path) {
         // Read all lines from filename and convert into a Stream of
-        // Strings.  The "try-with-resources" statement endures the
+        // Strings.  The "try-with-resources" statement ensures the
         // Stream cleanup is done automatically!
         try (Stream<String> lines = Files.lines(Paths.get(path))) {
             return lines
+                // Convert the stream into a parallel stream.
+                .parallel()
+
                 // Consume the first line, which gives the format of
                 // the CSV file.
                 .skip(1)

Java8/ex41/src/main/java/ex41.java

@@ -25,15 +25,21 @@ class ex41 {
      * @return The modified {@link List} of URLs
      */
     private static List<String> java7Replace(List<String> urls) {
+        // Make a copy of the urls.
         urls = new ArrayList<>(urls);
 
+        // Loop through all the urls.
         for (int i = 0; i < urls.size(); ++i) {
+            // Remove the url at index 'i' if it doesn't
+            // match what's expected.
             if (!urls.get(i).contains("cse.wustl")) {
                 urls.remove(i);
                 continue;
             }
+            // Replace the url at index 'i'.
             urls.set(i,
-                     urls.get(i).replace("cse.wustl","dre.vanderbilt"));
+                     urls.get(i).replace("cse.wustl",
+                             "dre.vanderbilt"));
         }
         return urls;
     }
@@ -46,9 +52,17 @@ private static List<String> java7Replace(List<String> urls) {
      */
     private static List<String> modernJavaReplace(List<String> urls) {
         return urls
+            // Convert the List to a Stream.
             .stream()
+
+            // Remove items from the Stream if they don't match what's expected.
             .filter(s -> s.contains("cse.wustl"))
+
+            // Perform the replacement on each item remaining in the stream.
             .map(s -> s.replace("cse.wustl", "dre.vanderbilt"))
+
+            // Trigger intermediate processing and collect the results
+            // into a List.
             .collect(toList());
     }
 
@@ -60,8 +74,11 @@ public static void main (String[] argv) {
         List<String> list = Arrays.asList(sUrlArray);
         System.out.println(list);
 
-        // Perform the replacements and print the results.
+        // Perform the Java 7 replacements and print the results.
         System.out.println(java7Replace(list));
+
+        System.out.println(list);
+        // Perform the modern Java replacements and print the results.
         System.out.println(modernJavaReplace((list)));
     }
 }

Java8/ex7/.run/ex7.run.xml

@@ -1,6 +1,6 @@
 <component name="ProjectRunConfigurationManager">
   <configuration default="false" name="ex7" type="Application" factoryName="Application">
-    <option name="ALTERNATIVE_JRE_PATH" value="corretto-11" />
+    <option name="ALTERNATIVE_JRE_PATH" value="openjdk-18" />
     <option name="ALTERNATIVE_JRE_PATH_ENABLED" value="true" />
     <option name="MAIN_CLASS_NAME" value="CrDemo$CrDemoEx" />
     <module name="Example 7" />

Java8/ex7/src/CrDemo.java

@@ -1,47 +1,12 @@
 import java.util.function.Supplier;
 
-/**
- * This example of shows how the Java functional interfaces (including
- * {@link Supplier} and a custom functional interface) can be used in
- * conjunction with Java constructor references.
- */
 public class CrDemo
        implements Runnable {
-    /**
-     * This class extends {@link CrDemo} and overrides its {@code
-     * run()} method to uppercase the string.
-     */
-    private static class CrDemoEx
-            extends CrDemo {
-        /**
-         * Constructor.
-         */
-        CrDemoEx() {
-            super();
-        }
-
-        /**
-         * Print the upper-cased value of mString.
-         */
-        @Override
-        public void run() {
-            System.out.println(mString.toUpperCase());
-        }
-    }
-
     /**
      * A field that stores a string.
      */
     String mString;
 
-    /**
-     * Main entry point into this program.
-     */
-    public static void main(String[] argv) {
-        zeroParamConstructorRef();
-        threeParamConstructorRef();
-    }
-
     /**
      * Default constructor.
      */
@@ -58,88 +23,12 @@ private CrDemo(String s, Integer i, Long l) {
         mString = s + i + l;
     }
 
-    /**
-     * Demonstrate how a {@link Supplier} can be used as a factory for
-     * a zero-parameter constructor reference.
-     */
-    private static void zeroParamConstructorRef() {
-        // Assign a constructor reference to a supplier that acts as a
-        // factory for a zero-param object of CrDemo.
-        Supplier<CrDemo> factory = CrDemo::new;
-
-        // Use the factory to create a new instance of CrDemo and call
-        // its run() method.
-        CrDemo crDemo = factory.get();
-        crDemo.run();
-    }
-
-    /**
-     * Demonstrate how {@link Supplier} objects can be used as
-     * factories for multiple zero-parameter constructor references.
-     */
-    private static void zeroParamConstructorRefEx() {
-        // Assign a constructor reference to a supplier that acts as a
-        // factory for a zero-param object of CrDemo.
-        Supplier<CrDemo> crDemoFactory = CrDemo::new;
-
-        // Assign a constructor reference to a supplier that acts as a
-        // factory for a zero-param object of CrDemoEx.
-        Supplier<CrDemoEx> crDemoFactoryEx = CrDemoEx::new;
-
-        // This helper method invokes the given supplier to create a
-        // new object and call its run() method.
-        runDemo(crDemoFactory);
-        runDemo(crDemoFactoryEx);
-    }
-
-    /**
-     * Use the given {@code factory} to create a new object and call
-     * its {@code run()} method.
-     */
-    private static <T extends Runnable> void runDemo(Supplier<T> factory) {
-        factory.get().run();
-    }
-
     /**
      * Print the value of mString.
      */
     @Override
     public void run() {
         System.out.println(mString);
     }
-
-    /**
-     * Demonstrate how a custom functional interface (i.e., {@link
-     * TriFactor}, which is defined below) can be used as a factory
-     * for a three-parameter constructor reference.
-     */
-    private static void threeParamConstructorRef() {
-        // Assign a constructor reference to a customized functional
-        // interface that acts as a factory to create a
-        // three-parameter constructor for CrDemo.
-        TriFactory<String, Integer, Long, CrDemo> factory = 
-            CrDemo::new;
-
-        // Use the factory to create a new instance of CrDemo and call
-        // its run() method.
-        factory.of("The answer is ", 4, 2L).run();
-    }
-
-    /**
-     * Represents a factory that accepts three arguments and produces
-     * a result.  This is a functional interface whose abstract method
-     * is {@link #of(Object, Object, Object)}.
-     */
-    @FunctionalInterface
-    interface TriFactory<P1,
-                         P2,
-                         P3,
-                         R> {
-        /**
-         * Create an object of type {@code R} using the three
-         * parameters and return the object.
-         */
-        R of(P1 p1, P2 p2, P3 p3);
-    }
 } 
 

Java8/ex7/src/CrDemoEx.java

@@ -0,0 +1,22 @@
+/**
+ * This class extends {@link CrDemo} and overrides its {@code run()}
+ * method to uppercase the string.
+ */
+public class CrDemoEx
+       extends CrDemo {
+    /**
+     * Constructor.
+     */
+    CrDemoEx() {
+        super();
+    }
+
+    /**
+     * Print the upper-cased value of mString.
+     */
+    @Override
+    public void run() {
+        System.out.println(mString.toUpperCase());
+    }
+}
+

Java8/ex7/src/ex7.java

@@ -0,0 +1,99 @@
+import java.util.function.Supplier;
+
+/**
+ * This example of shows how the Java functional interfaces (including
+ * {@link Supplier} and a custom functional interface) can be used in
+ * conjunction with Java constructor references.
+ */
+public class ex7 {
+    /**
+     * Main entry point into this program.
+     */
+    public static void main(String[] argv) {
+        zeroParamConstructorRef();
+        zeroParamConstructorRefEx();
+        threeParamConstructorRef();
+    }
+
+    /**
+     * Demonstrate how a {@link Supplier} can be used as a factory for
+     * a zero-parameter constructor reference.
+     */
+    private static void zeroParamConstructorRef() {
+        System.out.println("zeroParamConstructorRef()");
+
+        // Assign a constructor reference to a supplier that acts as a
+        // factory for a zero-param object of CrDemo.
+        Supplier<CrDemo> factory = CrDemo::new;
+
+        // Use the factory to create a new instance of CrDemo and call
+        // its run() method.
+        CrDemo crDemo = factory.get();
+        crDemo.run();
+    }
+
+    /**
+     * Demonstrate how {@link Supplier} objects can be used as
+     * factories for multiple zero-parameter constructor references.
+     */
+    private static void zeroParamConstructorRefEx() {
+        System.out.println("zeroParamConstructorRefEx()");
+
+        // Assign a constructor reference to a supplier that acts as a
+        // factory for a zero-param object of CrDemo.
+        Supplier<CrDemo> crDemoFactory = CrDemo::new;
+
+        // Assign a constructor reference to a supplier that acts as a
+        // factory for a zero-param object of CrDemoEx.
+        Supplier<CrDemoEx> crDemoFactoryEx = CrDemoEx::new;
+
+        // This helper method invokes the given supplier to create a
+        // new object and call its run() method.
+        runDemo(crDemoFactory);
+        runDemo(crDemoFactoryEx);
+    }
+
+    /**
+     * Use the given {@code factory} to create a new object and call
+     * its {@code run()} method.
+     */
+    private static <T extends Runnable> void runDemo(Supplier<T> factory) {
+        factory.get().run();
+    }
+
+    /**
+     * Represents a factory that accepts three arguments and produces
+     * a result.  This is a functional interface whose abstract method
+     * is {@link #of(Object, Object, Object)}.
+     */
+    @FunctionalInterface
+    interface TriFactory<P1,
+                         P2,
+                         P3,
+                         R> {
+        /**
+         * Create an object of type {@code R} using the three
+         * parameters and return the object.
+         */
+        R of(P1 p1, P2 p2, P3 p3);
+    }
+
+    /**
+     * Demonstrate how a custom functional interface (i.e., {@link
+     * TriFactory}, which is defined below) can be used as a factory
+     * for a three-parameter constructor reference.
+     */
+    public static void threeParamConstructorRef() {
+        System.out.println("threeParamConstructorRef()");
+
+        // Assign a constructor reference to a customized functional
+        // interface that acts as a factory to create a
+        // three-parameter constructor for CrDemo.
+        TriFactory<String, Integer, Long, CrDemo> factory = 
+            CrDemo::new;
+
+        // Use the factory to create a new instance of CrDemo and call
+        // its run() method.
+        factory.of("The answer is ", 4, 2L).run();
+    }
+}