Help with ANTLR

Hi All,

I am learning to use ANTLR and in trying out some stuff cannot work out
how to
parse for strings. My test grammar is as follows:

On trying an example, I am getting the error:

java -classpath /usr/java/lib/antlr.jar:. ExprParser '"joe";'
Exception in thread "main" line 1:2: expecting '"', found 'j'
        at ExprLexer.nextToken(ExprLexer.java:80)
        at antlr.TokenBuffer.fill(TokenBuffer.java:69)
        at antlr.TokenBuffer.LA(TokenBuffer.java:80)
        at antlr.LLkParser.LA(LLkParser.java:52)
        at ExprParser.stmt(ExprParser.java:61)
        at ExprParser.main(ExprParser.java:27)

Please help.
KM

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{   
    im****t java.io.StringReader;
}

class ExprParser extends Parser;
options {
    // buildAST = true;
}

{   
    public static void main(String[] args) throws Exception
    {   
        for (int i = 0 ; i < args.length ; i++ ) {
            ExprLexer lexer = new ExprLexer(new StringReader(args[i]));
            ExprParser parser = new ExprParser(lexer);
            parser.stmt();
        }
    }
}

stmt
    :   
        ( expr SEMI! )*
    ;

expr
    :   
        atom ( PLUS atom )*
    ;

atom
    :   
        STRING
    ;

class ExprLexer extends Lexer;

options {
    // k = 2;
    // charVocabulary = '\u0000' .. '\u00ff';
}

STRING
    :   
        '"'! ( ESCAPE | ~('"'|'\\') )* '"'!
    ;

protected ESCAPE
    :   
        '\\'
        (   
            'n' { $setText("\n"); }
            'r' { $setText("\r"); }
            't' { $setText("\t"); }
            '"' { $setText("\""); }
        )
    ;

WS: ( ' ' | '\r' '\n' | '\n' | '\t' ) { $setType( Token.SKIP ); };

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