Fix warnings

pf4j/src/main/java/org/pf4j/BasePluginRepository.java

         this.filter = filter;
 
         // last modified file is first
-        this.comparator = new Comparator<File>() {
-
-            @Override
-            public int compare(File o1, File o2) {
-                return (int) (o2.lastModified() - o1.lastModified());
-            }
-
-        };
+        this.comparator = (o1, o2) -> (int) (o2.lastModified() - o1.lastModified());
     }
 
     public void setFilter(FileFilter filter) {

pf4j/src/main/java/org/pf4j/ManifestPluginDescriptorFinder.java

         }
     }
 
-    protected Path getManifestPath(Path pluginPath) throws PluginException {
+    protected Path getManifestPath(Path pluginPath) {
         if (Files.isDirectory(pluginPath)) {
             // legacy (the path is something like "classes/META-INF/MANIFEST.MF")
             return FileUtils.findFile(pluginPath,"MANIFEST.MF");

pf4j/src/main/java/org/pf4j/PluginWrapper.java

         }
 
         PluginWrapper other = (PluginWrapper) obj;
-        if (!descriptor.getPluginId().equals(other.descriptor.getPluginId())) {
-            return false;
-        }
 
-        return true;
+        return descriptor.getPluginId().equals(other.descriptor.getPluginId());
+
     }
 
     @Override

pf4j/src/main/java/org/pf4j/processor/ExtensionAnnotationProcessor.java

             String extension = getBinaryName(extensionElement);
             for (TypeElement extensionPointElement : extensionPointElements) {
                 String extensionPoint = getBinaryName(extensionPointElement);
-                Set<String> extensionPoints = extensions.get(extensionPoint);
-                if (extensionPoints == null) {
-                    extensionPoints = new TreeSet<>();
-                    extensions.put(extensionPoint, extensionPoints);
-                }
+                Set<String> extensionPoints = extensions.computeIfAbsent(extensionPoint, k -> new TreeSet<>());
                 extensionPoints.add(extension);
             }
         }

pf4j/src/main/java/org/pf4j/util/AndFileFilter.java

 import java.util.List;
 
 /**
- * This filter providing conditional AND logic across a list of
- * file filters. This filter returns <code>true</code> if all filters in the
- * list return <code>true</code>. Otherwise, it returns <code>false</code>.
- * Checking of the file filter list stops when the first filter returns
- * <code>false</code>.
+ * This filter providing conditional AND logic across a list of file filters.
+ * This filter returns {@code true} if all filters in the list return {@code true}. Otherwise, it returns {@code false}.
+ * Checking of the file filter list stops when the first filter returns {@code false}.
  *
  * @author Decebal Suiu
  */
     private List<FileFilter> fileFilters;
 
     public AndFileFilter() {
-        this(new ArrayList<FileFilter>());
+        this(new ArrayList<>());
     }
 
     public AndFileFilter(FileFilter... fileFilters) {
 
     @Override
     public boolean accept(File file) {
-        if (this.fileFilters.size() == 0) {
+        if (this.fileFilters.isEmpty()) {
             return false;
         }
 

pf4j/src/main/java/org/pf4j/util/DirectedGraph.java

             return;
         }
 
-        neighbors.put(vertex, new ArrayList<V>());
+        neighbors.put(vertex, new ArrayList<>());
     }
 
     /**
     }
 
     public List<V> getNeighbors(V vertex) {
-        return containsVertex(vertex) ? neighbors.get(vertex) : new ArrayList<V>();
+        return containsVertex(vertex) ? neighbors.get(vertex) : new ArrayList<>();
     }
 
     /**
     }
 
     /**
-     * Report (as a Map) the in-degree (the number of head ends adjacent to a vertex) of each vertex.
+     * Report (as a {@link Map}) the in-degree (the number of head ends adjacent to a vertex) of each vertex.
      */
     public Map<V, Integer> inDegree() {
         Map<V, Integer> result = new HashMap<>();
      */
     @Override
     public String toString() {
-        StringBuffer sb = new StringBuffer();
+        StringBuilder sb = new StringBuilder();
         for (V vertex : neighbors.keySet()) {
-            sb.append("\n   " + vertex + " -> " + neighbors.get(vertex));
+            sb.append("\n   ").append(vertex).append(" -> ").append(neighbors.get(vertex));
         }
 
         return sb.toString();

pf4j/src/main/java/org/pf4j/util/OrFileFilter.java

 import java.util.List;
 
 /**
- * This filter providing conditional OR logic across a list of
- * file filters. This filter returns <code>true</code> if one filter in the
- * list return <code>true</code>. Otherwise, it returns <code>false</code>.
- * Checking of the file filter list stops when the first filter returns
- * <code>true</code>.
+ * This filter providing conditional OR logic across a list of file filters.
+ * This filter returns {@code true} if one filter in the list return {@code true}. Otherwise, it returns {@code false}.
+ * Checking of the file filter list stops when the first filter returns {@code true}.
  *
  * @author Decebal Suiu
  */
     private List<FileFilter> fileFilters;
 
     public OrFileFilter() {
-        this(new ArrayList<FileFilter>());
+        this(new ArrayList<>());
     }
 
     public OrFileFilter(FileFilter... fileFilters) {
 
     @Override
     public boolean accept(File file) {
-        if (this.fileFilters.size() == 0) {
+        if (this.fileFilters.isEmpty()) {
             return true;
         }