a simple get-started javacc example

create a grammar file

PARSER_BEGIN(Hello)
package egtry.hello;

import java.io.StringReader;

public class Hello {
  
    public static void main(String[] args) throws Exception {
      StringReader in=new StringReader("count 10");
      Hello hello=new Hello(in);
      Hello.words();
    }
    
}

PARSER_END(Hello)



SKIP: { " " |"\t" |"\n" |"\r" }

TOKEN: { <WORD: (["a"-"z"])+ > }
TOKEN: { <INT: (["0"-"9"])+ >  }

void words():
{
  int id=0;
}
{
  <WORD> 
      { id++; 
        System.out.println(id+" word"); 
      }
  <INT>
     {
       id++;
       System.out.println(id+"id");
     }
   <EOF>
}

Compile hello.jj and generate java codes

 java -classpath "\java\javacc-5.0\bin\lib\javacc.jar" javacc hello.jj

Run the Hello.java

1 word
2id

Generated the Hello.java source

package egtry.hello; //copied from the grammar file
import java.io.StringReader; //copied from the grammar file

public class Hello implements HelloConstants {

   //copied from the grammar file
    public static void main(String[] args) throws Exception {
      StringReader in=new StringReader("count 10");
      Hello hello=new Hello(in);
      Hello.words();
    }

  static final public void words() throws ParseException {
  int id=0; //copied from the rule init block
    jj_consume_token(WORD);
        id++; //copied from production action
        System.out.println(id+" word");
    jj_consume_token(INT);
       id++;
       System.out.println(id+"id");
    jj_consume_token(0); //EOF
  }
 ....
}