Merge pull request #5 from ravening/feature/functional-java-refactor

Refactor multithreading example to functional style

Author: ravening

classes/main/java/multithreading/AppleTree.class

@@ -1,19 +1,17 @@
 package main.java.multithreading;
 
-import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.IntStream;
 
 public class AppleTree {
     private final String treeLabel;
     private final int numberOfApples;
 
     public static AppleTree[] newTreeGarden(int size) {
-        AppleTree[] appleTrees = new AppleTree[size];
-        for (int i = 0; i < appleTrees.length; i++) {
-            appleTrees[i] = new AppleTree("🌳#" + i);
-        }
-        return appleTrees;
+        return IntStream.range(0, size)
+                .mapToObj(i -> new AppleTree("🌳#" + i))
+                .toArray(AppleTree[]::new);
     }
 
     public AppleTree(String treeLabel) {
@@ -37,12 +35,11 @@ public int pickApples() {
     }
 
     private String toLabel(String threadName) {
-        Map<String, String> threadNameToLabel = new HashMap<>();
-        threadNameToLabel.put("ForkJoinPool.commonPool-worker-1", "Alice");
-        threadNameToLabel.put("ForkJoinPool.commonPool-worker-2", "Bob");
-        threadNameToLabel.put("ForkJoinPool.commonPool-worker-3", "Carol");
-        threadNameToLabel.put("ForkJoinPool.commonPool-worker-4", "Dan");
-
-        return threadNameToLabel.getOrDefault(threadName, threadName);
+        return Map.of(
+                "ForkJoinPool.commonPool-worker-1", "Alice",
+                "ForkJoinPool.commonPool-worker-2", "Bob",
+                "ForkJoinPool.commonPool-worker-3", "Carol",
+                "ForkJoinPool.commonPool-worker-4", "Dan"
+        ).getOrDefault(threadName, threadName);
     }
 }

classes/main/java/multithreading/ForkJoinExample.class

@@ -1,9 +1,9 @@
 package main.java.multithreading;
 
+import java.util.List;
 import java.util.concurrent.Callable;
 import java.util.concurrent.ForkJoinPool;
-
-import static java.util.Arrays.asList;
+import java.util.stream.IntStream;
 
 public class ForkJoinExample {
     public static void main(String[] args) {
@@ -13,7 +13,7 @@ public static void main(String[] args) {
         Callable<Void> applePicker2 = createApplePicker(appleTrees, 2, 4, "Bob");
         Callable<Void> applePicker3 = createApplePicker(appleTrees, 4, 6, "Carol");
 
-        ForkJoinPool.commonPool().invokeAll(asList(applePicker1, applePicker2, applePicker3));
+        ForkJoinPool.commonPool().invokeAll(List.of(applePicker1, applePicker2, applePicker3));
 
         System.out.println();
         System.out.println("All fruits collected!");
@@ -22,9 +22,8 @@ public static void main(String[] args) {
     public static Callable<Void> createApplePicker(AppleTree[] appleTrees, int fromIndexInclusive, int toIndexExclusive,
                                                    String workerName) {
         return () -> {
-            for (int i = fromIndexInclusive; i < toIndexExclusive; i++) {
-                appleTrees[i].pickApples(workerName);
-            }
+            IntStream.range(fromIndexInclusive, toIndexExclusive)
+                    .forEach(i -> appleTrees[i].pickApples(workerName));
             return null;
         };
     }