[java] Parser Error for empty statements

Fixes #378

pmd-java/etc/grammar/Java.jjt

@@ -1,4 +1,9 @@
 /**
+ * Allow empty statements (";") between package, import
+ * and type declarations.
+ * Bug #378
+ * Andreas Dangel 05/2017
+ *====================================================================
  * Allow method references to specify generics also for
  * constructor references ("new").
  * Bug #309
@@ -1252,9 +1257,9 @@ TOKEN :
 ASTCompilationUnit CompilationUnit() :
 {}
 {
-  [ LOOKAHEAD( ( Annotation() )* "package" ) PackageDeclaration() ]
-  ( ImportDeclaration() )*
-  ( TypeDeclaration() )*
+  [ LOOKAHEAD( ( Annotation() )* "package" ) PackageDeclaration() ( EmptyStatement() )* ]
+  ( ImportDeclaration() ( EmptyStatement() )* )*
+  ( TypeDeclaration() ( EmptyStatement() )* )*
   ( < "\u001a" > )?
   ( < "~[]" > )?
   <EOF>
@@ -1317,8 +1322,6 @@ void TypeDeclaration():
    int modifiers;
 }
 {
-  ";"
-|
   modifiers = Modifiers()
   (
      ClassOrInterfaceDeclaration(modifiers)

pmd-java/src/test/java/net/sourceforge/pmd/lang/java/ast/ParserCornersTest.java

@@ -194,6 +194,29 @@ public class ParserCornersTest extends ParserTst {
         Assert.assertEquals(0, cu.findDescendantsOfType(ASTCastExpression.class).size());
     }
 
+    /**
+     * Empty statements should be allowed.
+     * @throws Exception
+     * @see https://github.com/pmd/pmd/issues/378
+     */
+    @Test
+    public void testParseEmptyStatements() throws Exception {
+        String code = "import a;;import b; public class Foo {}";
+        ASTCompilationUnit cu = parseJava18(code);
+        assertNotNull(cu);
+        Assert.assertEquals(ASTEmptyStatement.class, cu.jjtGetChild(1).getClass());
+
+        String code2 = "package c;; import a; import b; public class Foo {}";
+        ASTCompilationUnit cu2 = parseJava18(code2);
+        assertNotNull(cu2);
+        Assert.assertEquals(ASTEmptyStatement.class, cu2.jjtGetChild(1).getClass());
+
+        String code3 = "package c; import a; import b; public class Foo {};";
+        ASTCompilationUnit cu3 = parseJava18(code3);
+        assertNotNull(cu3);
+        Assert.assertEquals(ASTEmptyStatement.class, cu3.jjtGetChild(4).getClass());
+    }
+
     private String readAsString(String resource) {
         InputStream in = ParserCornersTest.class.getResourceAsStream(resource);
         try {

src/site/markdown/overview/changelog.md

@@ -38,6 +38,8 @@ This is a minor release.
 *   General
     *   [#377](https://github.com/pmd/pmd/issues/377): \[core] Use maven wrapper and upgrade to maven 3.5.0
     *   [#376](https://github.com/pmd/pmd/issues/376): \[core] Improve build time on travis
+*   java
+    *   [#378](https://github.com/pmd/pmd/issues/378): \[java] Parser Error for empty statements
 *   java-coupling
     *   [#1427](https://sourceforge.net/p/pmd/bugs/1427/): \[java] Law of Demeter violations for the Builder pattern
 *   java-design