added ex Q2

src/exercises/ex_q2/CustomRecursiveAction.java

@@ -0,0 +1,34 @@
+package exercises.ex_q2;
+
+import java.util.concurrent.RecursiveAction;
+import java.util.logging.Logger;
+
+public class CustomRecursiveAction extends RecursiveAction {
+    private static final int threshold = 10;
+    private String song;
+
+    public CustomRecursiveAction(String song) {
+        this.song = song;
+    }
+
+    @Override
+    protected void compute() {
+        Logger logger = Logger.getAnonymousLogger();
+        if (song.length() <= threshold) {
+            logger.info("Splitting problem");
+            changeToUppercase();
+        } else {
+            logger.info("Problem is small enough");
+            int halfSize = song.length() / 2;
+            CustomRecursiveAction task1 = new CustomRecursiveAction(song.substring(0, halfSize));
+            CustomRecursiveAction task2 = new CustomRecursiveAction(song.substring(halfSize));
+            invokeAll(task1, task2);
+            song = task1.song + task2.song;
+            logger.info("Solution: " + song);
+        }
+    }
+
+    protected void changeToUppercase() {
+        song = song.toUpperCase();
+    }
+}

src/exercises/ex_q2/ForkJoinTest.java

@@ -0,0 +1,28 @@
+package exercises.ex_q2;
+
+import java.util.concurrent.ForkJoinPool;
+
+public class ForkJoinTest {
+    public static void main(String[] args) {
+        String song = "Georges Brassens (1964) - Les Copains d'abord"
+            + "Non, ce n'était pas le radeau"
+            + "De la Méduse, ce bateau"
+            + "Qu'on se le dise au fond des ports"
+            + "Dise au fond des ports"
+            + "Il naviguait en père peinard"
+            + "Sur la grand-mare des canards"
+            + "Et s'appelait les Copains d'abord"
+            + "Les Copains d'abord";
+        int processors = Runtime.getRuntime().availableProcessors();
+        System.out.println("Number of available processors: " + processors);
+        ForkJoinPool pool = new ForkJoinPool(processors);
+        long startTime = System.currentTimeMillis();
+        pool.invoke(new CustomRecursiveAction(song));
+        long endTime = System.currentTimeMillis();
+        System.out.println(
+            "Fork/Join tasks took "
+                + (endTime - startTime)
+                + " milliseconds."
+        );
+    }
+}