antl3:Java heap space when testing parser - antlr3

Question

I'm trying to build a simple config-file reader to read files of this format:
A .-
B -...
C -.-.
D -..
E .
This is the grammar I have so far:
grammar def;
#header {
package mypackage.parser;
}
#lexer::header { package mypackage.parser; }
file
: line+;
line : ID WS* CODE NEWLINE;
ID : ('A'..'Z')*
;
CODE : ('-'|'.')*;
COMMENT
: '//' ~('\n'|'\r')* '\r'? '\n' {$channel=HIDDEN;}
| '/*' ( options {greedy=false;} : . )* '*/' {$channel=HIDDEN;}
;
WS : ( ' '
| '\t'
) {$channel=HIDDEN;}
;
NEWLINE:'\r'? '\n' ;
And this is my test rig (junit4)
#Test
public void BasicGrammarCheckGood() {
String CorrectlyFormedLine="A .-;\n";
ANTLRStringStream input;
defLexer lexer;
defParser parser;
input = new ANTLRStringStream(CorrectlyFormedLine);
lexer = new defLexer(input);
CommonTokenStream tokens = new CommonTokenStream(lexer);
parser = new defParser(tokens);
try {
parser.line();
}
catch(RecognitionException re) { fail(re.getMessage()); }
}
If I run this test right with a corrected formatted string - the code exits without any exception or output.
However if feed the parser with an invalid string like this : "xA .-;\n", the code spins for a while then exits with a "Java heap space".
(If I start my test with the top-level rule 'file', then I get the same result - with the additional (repeated) output of "line 1:0 mismatched input '' expecting CODE")
What's going wrong here ? I never seem to get the "RecognitionException" for the invalid output ?
EDIT: Here's my grammar file (Fragment), after being provided advice here - this avoids the 'Java heap space' issue.
file
: line+ EOF;
line : ID WS* CODE NEWLINE;
ID : ('A'..'Z')('A'..'Z')*
;
CODE : ('-'|'.')('-'|'.')*;

Answer 1

Some of your lexer rules match zero characters (an empty string):
ID : ('A'..'Z')*
;
CODE : ('-'|'.')*;
There are, of course, an infinite amount of empty strings in your input, causing your lexer to keep producing tokens, resulting in a heap space error after a while.
Always let lexer rules match at least 1 character.
EDIT
Two (small) remarks:
since you put the WS token on the hidden channel, you don't need to add them in your parser rules. So line becomes line : ID CODE NEWLINE;
something like ('A'..'Z')('A'..'Z')* can be written like this: ('A'..'Z')+