asyncronous channel apis (#839)

* made changes to java reflection

* removed redundant method makeSound in Animal abstract class

* added project for play-framework article

* added project for regex

* changed regex project from own model to core-java

* added project for routing in play

* made changes to regex project

* refactored code for REST API with Play project

* refactored student store indexing to zero base

* added unit tests, removed bad names

* added NIO Selector project under core-java module

* requested changes made

* added project for nio2

* standardized exception based tests

* fixed exception based tests

* removed redundant files

* added network interface project

* used UUID other than timestamps

* fixed network interface tests

* removed filetest change

* made changes to NIO2 FileTest names

* added project for asyncronous channel apis

* added project for NIO2 advanced filesystems APIS

core-java/src/main/java/com/baeldung/java/nio2/visitor/FileSearchExample.java

@@ -0,0 +1,60 @@
+package com.baeldung.java.nio2.visitor;
+
+import static java.nio.file.FileVisitResult.CONTINUE;
+import static java.nio.file.FileVisitResult.TERMINATE;
+
+import java.io.IOException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.FileVisitor;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.attribute.BasicFileAttributes;
+
+public class FileSearchExample implements FileVisitor<Path> {
+    private static String FILE_NAME;
+    private static Path START_DIR;
+
+    public FileSearchExample(String fileName, Path startingDir) {
+        FILE_NAME = fileName;
+        START_DIR = startingDir;
+    }
+
+    @Override
+    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
+        return CONTINUE;
+    }
+
+    @Override
+    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
+        String fileName = file.getFileName().toString();
+        if (FILE_NAME.equals(fileName)) {
+            System.out.println("File found: " + file.toString());
+            return TERMINATE;
+        }
+        return CONTINUE;
+    }
+
+    @Override
+    public FileVisitResult visitFileFailed(Path file, IOException exc) throws IOException {
+        System.out.println("Failed to access file: " + file.toString());
+        return CONTINUE;
+    }
+
+    @Override
+    public FileVisitResult postVisitDirectory(Path dir, IOException exc) throws IOException {
+        boolean finishedSearch = Files.isSameFile(dir, START_DIR);
+        if (finishedSearch) {
+            System.out.println("File:" + FILE_NAME + " not found");
+            return TERMINATE;
+        }
+        return CONTINUE;
+    }
+
+    public static void main(String[] args) throws IOException {
+        Path startingDir = Paths.get("C:/Users/new/Desktop");
+        FileSearchExample crawler = new FileSearchExample("hibernate.txt", startingDir);
+        Files.walkFileTree(startingDir, crawler);
+    }
+
+}

core-java/src/main/java/com/baeldung/java/nio2/visitor/FileVisitorImpl.java

@@ -0,0 +1,30 @@
+package com.baeldung.java.nio2.visitor;
+
+import java.io.IOException;
+import java.nio.file.FileVisitResult;
+import java.nio.file.FileVisitor;
+import java.nio.file.Path;
+import java.nio.file.attribute.BasicFileAttributes;
+
+public class FileVisitorImpl implements FileVisitor<Path> {
+
+    @Override
+    public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) {
+        return null;
+    }
+
+    @Override
+    public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) {
+        return null;
+    }
+
+    @Override
+    public FileVisitResult visitFileFailed(Path file, IOException exc) {       
+        return null;
+    }
+
+    @Override
+    public FileVisitResult postVisitDirectory(Path dir, IOException exc) {    
+        return null;
+    }
+}

core-java/src/main/java/com/baeldung/java/nio2/watcher/DirectoryWatcherExample.java

@@ -0,0 +1,25 @@
+package com.baeldung.java.nio2.watcher;
+
+import java.io.IOException;
+import java.nio.file.FileSystems;
+import java.nio.file.Path;
+import java.nio.file.Paths;
+import java.nio.file.StandardWatchEventKinds;
+import java.nio.file.WatchEvent;
+import java.nio.file.WatchKey;
+import java.nio.file.WatchService;
+
+public class DirectoryWatcherExample {
+    public static void main(String[] args) throws IOException, InterruptedException {
+        WatchService watchService = FileSystems.getDefault().newWatchService();
+        Path path = Paths.get(System.getProperty("user.home"));
+        path.register(watchService, StandardWatchEventKinds.ENTRY_CREATE, StandardWatchEventKinds.ENTRY_DELETE, StandardWatchEventKinds.ENTRY_MODIFY);
+        WatchKey key;
+        while ((key = watchService.take()) != null) {
+            for (WatchEvent<?> event : key.pollEvents()) {
+                System.out.println("Event kind:" + event.kind() + ". File affected: " + event.context() + ".");
+            }
+            key.reset();
+        }
+    }
+}