Replace some anonymous classes with lambdas

core/src/main/java/hudson/ClassicPluginStrategy.java

@@ -83,12 +83,7 @@ public class ClassicPluginStrategy implements PluginStrategy {
     /**
      * Filter for jar files.
      */
-    private static final FilenameFilter JAR_FILTER = new FilenameFilter() {
-        @Override
-        public boolean accept(File dir,String name) {
-            return name.endsWith(".jar");
-        }
-    };
+    private static final FilenameFilter JAR_FILTER = (dir, name) -> name.endsWith(".jar");
 
     private PluginManager pluginManager;