Fixes #793 [java] Parser error with private method in nested classes in interfaces

pmd-java/etc/grammar/Java.jjt

@@ -1,4 +1,7 @@
 /**
+ * Fixes #793 [java] Parser error with private method in nested classes in interfaces
+ * Andreas Dangel 12/2017
+ *====================================================================
  * Add support for Java 9 changes:
  * Private interface methods are only allowed with java9.
  * A single underscore "_" is an invalid identifier in java9.
@@ -340,6 +343,7 @@ public class JavaParser {
    * Keeps track whether we are dealing with an interface or not. Needed since the tree is
    * is not fully constructed yet, when we check for private interface methods.
    * The flag is updated, if entering ClassOrInterfaceDeclaration and reset when leaving.
+   * The flag is also reset, if entering a anonymous inner class.
    */
   private boolean inInterface = false;
   private void checkForBadPrivateInterfaceMethod(ASTMethodDeclaration node) {
@@ -2009,7 +2013,7 @@ void AllocationExpression():
      (
       ArrayDimsAndInits()
      |
-      Arguments() [ ClassOrInterfaceBody() ]
+      Arguments() [ {inInterface = false;} ClassOrInterfaceBody() ]
      )
   )
   { checkForBadAnonymousDiamondUsage(); }