Not able to parse continuos string using antlr (without spaces) - antlr

Question

I have to parse the following query using antlr
sys_nameLIKEvalue
Here sys_name is a variable which has lower case and underscores.
LIKE is a fixed key word.
value is a variable which can contain lower case uppercase as well as number.
Below the grammer rule i am using
**expression : parameter 'LIKE' values EOF;
parameter : (ID);
ID : (LOWERCASE) (LOWERCASE | UNDERSCORE)* ;
values : (VALUE);
VALUE : (LOWERCASE | NUMBER | UPPERCASE)+ ;
LOWERCASE : 'a'..'z' ;
UPPERCASE : 'A'..'Z' ;
NUMBER : '0'..'9' ;
UNDERSCORE : '_' ;**
Test Case 1
Input : sys_nameLIKEabc
error thrown : line 1:8 missing 'LIKE' at 'LIKEabc'
Test Case 2
Input : sysnameLIKEabc
error thrown : line 1:0 mismatched input 'sysnameLIKEabc' expecting ID

Answer 1

A literal token inside your parser rule will be translated into a plain lexer rule. So, your grammar really looks like this:
expression : parameter LIKE values EOF;
parameter : ID;
values : VALUE;
LIKE : 'LIKE';
ID : LOWERCASE (LOWERCASE | UNDERSCORE)* ;
VALUE : (LOWERCASE | NUMBER | UPPERCASE)+ ;
// Fragment rules will never become tokens of their own: good practice!
fragment LOWERCASE : 'a'..'z' ;
fragment UPPERCASE : 'A'..'Z' ;
fragment NUMBER : '0'..'9' ;
fragment UNDERSCORE : '_' ;
Since lexer rules are greedy, and if two or more lexer rules match the same amount of character the first will "win", your input is tokenized as follows:
Input: sys_nameLIKEabc, 2 tokens:
sys_name: ID
LIKEabc: VALUE
Input: sysnameLIKEabc, 1 token:
sys_nameLIKEabc: VALUE
So, the token LIKE will never be created with your test input, so none of your parser rule will ever match. It also seems a bit odd to parse input without any delimiters, like spaces.
To fix your issue, you will either have to introduce delimiters, or disallow your VALUE to contain uppercases.