„Erratic“ grammar parsing by JavaCC for the IfStatement?

Starting from the Java 1.1 grammar I have tried to write a simplified grammar for a new language. Trying to parse IfStatements in various shapes I have encountered a strange problem which I don’t understand and for which I can’t find a solution. I have written two test programs, the first containing:

…  if (a > b) { x = 15; } else { x = 30; } 

and the second:

…  if (a > b) x = 15; else  x = 30;  

The first program is parsed without any problems while for the second the parser stops with the message “Encountered else at (start of ELSE) expecting one of: boolean | break | byte | char | continue ... “. According to the grammar (or rather to my intention ) there shouldn’t be any difference between a block or a single statement, and to my astonishment this perfectly works for WHILE or DO but not for IF.

The relevant pieces of my grammar are as follows:

void Statement() :
{}
{
  ( LOOKAHEAD(2)
  Block()  |  EmptyStatement()  |  IfStatement()  |
  WhileStatement()  |  ...
}

void Block() :
{}
{  "{"   (   BlockStatement()   )*   "}"
}

void BlockStatement() :
{}
{
  ( LOOKAHEAD(2)  LocalVariableDeclaration() ";"  |
  Statement()
  )
}

void EmptyStatement() :
{}
{  ";"  }

void IfStatement() :
{}
{
  "if" "(" Expression() ")"   Statement()   
[ LOOKAHEAD(1) "else" Statement() ]
}

void WhileStatement() :
{}
{
  "while" "(" Expression() ")" Statement()
}

There is a second observation possibly connected with the above problem: As stated before, the first test program is parsed correctly. However, for the “Statement” in the (partial) grammar rule <"if" "(" Expression() ")" Statement()> in the IF statement the parser yields an overly complex sequence of “Statement, Block, BlockStatement, Statement” nodes including an EmptyStatement before and after the statement content while parsing a test program containing an equivalent WHILE loop just produces “Statement” and no EmptyStatements at all.

So far I have tried to increase the number of lookahead elements in the IfStatement and/or the Statement productions but without any effect.

What is going wrong here, or what is wrong in my grammar?