The second multithreading task

filescanner/src/FileCounterTask.java

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+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RecursiveTask;
+import java.util.concurrent.atomic.AtomicLong;
+
+public class FileCounterTask extends RecursiveTask<Long> {
+
+    /**
+     * Current processed file
+     */
+    protected final File mFile;
+    /**
+     * All documents in folder
+     */
+    protected final AtomicLong mDocumentCount;
+    /**
+     * Directories count
+     */
+    protected final AtomicLong mFolderCount;
+    FileCounterTask(File file, AtomicLong mDocumentCount, AtomicLong mFolderCount) {
+        this.mFile = file;
+        this.mDocumentCount = new AtomicLong(0);
+        this.mFolderCount = new AtomicLong(0);
+    }
+
+    /**
+     *
+     * @return files number
+     */
+    public AtomicLong documentCount() {
+        return mDocumentCount;
+    };
+
+    /**
+     *
+     * @return directories number
+     */
+    public AtomicLong folderCount() {
+        return mFolderCount;
+    }
+
+    @Override
+    protected Long compute() {
+        if (mFile.isFile()) {
+            mDocumentCount.incrementAndGet();
+        } else {
+            mFolderCount.incrementAndGet();
+        }
+
+        List<ForkJoinTask<Long>> forkJoinTaskList = new ArrayList<>();
+        for(File file: Objects.requireNonNull(mFile.listFiles())) {
+            //the task for each File
+            forkJoinTaskList.add(
+                    new FileCounterTask(file, mDocumentCount, mFolderCount).fork());
+        }
+
+        long sum = 0;
+
+        for (ForkJoinTask<Long> forkJoinTask: forkJoinTaskList) {
+            sum += forkJoinTask.join();
+        }
+
+        return sum;
+    }
+}