Minor improvements: (#233)

* Use Method reference
* Use List.sort()
* Change Explicit with <>
* Simplify conditional expression

Author: arturobernalg

src/main/java/org/apache/commons/io/FileCleaningTracker.java

@@ -52,11 +52,11 @@ public class FileCleaningTracker {
     /**
      * Collection of {@code Tracker} instances in existence.
      */
-    final Collection<Tracker> trackers = Collections.synchronizedSet(new HashSet<Tracker>()); // synchronized
+    final Collection<Tracker> trackers = Collections.synchronizedSet(new HashSet<>()); // synchronized
     /**
      * Collection of File paths that failed to delete.
      */
-    final List<String> deleteFailures = Collections.synchronizedList(new ArrayList<String>());
+    final List<String> deleteFailures = Collections.synchronizedList(new ArrayList<>());
     /**
      * Whether to terminate the thread when the tracking is complete.
      */

src/main/java/org/apache/commons/io/FileUtils.java

@@ -1507,7 +1507,7 @@ public static String getUserDirectoryPath() {
      * @since 2.9.0
      */
     public static boolean isDirectory(final File file, final LinkOption... options) {
-        return file != null ? Files.isDirectory(file.toPath(), options) : false;
+        return file != null && Files.isDirectory(file.toPath(), options);
     }
 
     /**
@@ -1681,7 +1681,7 @@ public static boolean isFileNewer(final File file, final Instant instant) {
      */
     public static boolean isFileNewer(final File file, final long timeMillis) {
         Objects.requireNonNull(file, "file");
-        return file.exists() ? lastModifiedUnchecked(file) > timeMillis : false;
+        return file.exists() && lastModifiedUnchecked(file) > timeMillis;
     }
 
     /**
@@ -1842,7 +1842,7 @@ public static boolean isFileOlder(final File file, final Instant instant) {
      */
     public static boolean isFileOlder(final File file, final long timeMillis) {
         Objects.requireNonNull(file, "file");
-        return file.exists() ? lastModifiedUnchecked(file) < timeMillis : false;
+        return file.exists() && lastModifiedUnchecked(file) < timeMillis;
     }
 
     /**
@@ -1860,7 +1860,7 @@ public static boolean isFileOlder(final File file, final long timeMillis) {
      * @since 2.9.0
      */
     public static boolean isRegularFile(final File file, final LinkOption... options) {
-        return file != null ? Files.isRegularFile(file.toPath(), options) : false;
+        return file != null && Files.isRegularFile(file.toPath(), options);
     }
 
     /**
@@ -1875,7 +1875,7 @@ public static boolean isRegularFile(final File file, final LinkOption... options
      * @see Files#isSymbolicLink(Path)
      */
     public static boolean isSymlink(final File file) {
-        return file != null ? Files.isSymbolicLink(file.toPath()) : false;
+        return file != null && Files.isSymbolicLink(file.toPath());
     }
 
     /**
@@ -2060,7 +2060,7 @@ public static LineIterator lineIterator(final File file, final String charsetNam
             inputStream = openInputStream(file);
             return IOUtils.lineIterator(inputStream, charsetName);
         } catch (final IOException | RuntimeException ex) {
-            IOUtils.closeQuietly(inputStream, e -> ex.addSuppressed(e));
+            IOUtils.closeQuietly(inputStream, ex::addSuppressed);
             throw ex;
         }
     }

src/main/java/org/apache/commons/io/IOUtils.java

@@ -180,12 +180,12 @@ public class IOUtils {
     /**
      * Internal byte array buffer.
      */
-    private static final ThreadLocal<byte[]> SKIP_BYTE_BUFFER = ThreadLocal.withInitial(() -> byteArray());
+    private static final ThreadLocal<byte[]> SKIP_BYTE_BUFFER = ThreadLocal.withInitial(IOUtils::byteArray);
 
     /**
      * Internal byte array buffer.
      */
-    private static final ThreadLocal<char[]> SKIP_CHAR_BUFFER = ThreadLocal.withInitial(() -> charArray());
+    private static final ThreadLocal<char[]> SKIP_CHAR_BUFFER = ThreadLocal.withInitial(IOUtils::charArray);
 
     /**
      * Returns the given InputStream if it is already a {@link BufferedInputStream}, otherwise creates a

src/main/java/org/apache/commons/io/LineIterator.java

@@ -105,7 +105,7 @@ public boolean hasNext() {
                 }
             }
         } catch(final IOException ioe) {
-            IOUtils.closeQuietly(this, e -> ioe.addSuppressed(e));
+            IOUtils.closeQuietly(this, ioe::addSuppressed);
             throw new IllegalStateException(ioe);
         }
     }

src/main/java/org/apache/commons/io/comparator/AbstractFileComparator.java

@@ -58,7 +58,7 @@ public File[] sort(final File... files) {
      */
     public List<File> sort(final List<File> files) {
         if (files != null) {
-            Collections.sort(files, this);
+            files.sort(this);
         }
         return files;
     }

src/main/java/org/apache/commons/io/file/PathUtils.java

@@ -733,7 +733,7 @@ public static List<AclEntry> getAclEntryList(final Path sourcePath) throws IOExc
      * @since 2.9.0
      */
     public static boolean isDirectory(final Path path, final LinkOption... options) {
-        return path != null ? Files.isDirectory(path, options) : false;
+        return path != null && Files.isDirectory(path, options);
     }
 
     /**
@@ -815,7 +815,7 @@ public static boolean isNewer(final Path file, final long timeMillis, final Link
      * @since 2.9.0
      */
     public static boolean isRegularFile(final Path path, final LinkOption... options) {
-        return path != null ? Files.isRegularFile(path, options) : false;
+        return path != null && Files.isRegularFile(path, options);
     }
 
     /**