Thread: Java error

Hey Everyone,

I'm doing an assignment for my computer science course and I got stuck on an error and just thought you might make it clearer for me, i'm not asking that you do anything more than make it clearer, although i appreciate any extra help,

this is my code:

import java.io.File;
import java.io.FileNotFoundException;
import java.io.PrintStream;
import java.util.Scanner;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
public class Parser
{
  private boolean success;
  private Parser.Scanner scanner;
 
  private Parser()
  {
  }
 
  public Parser(String paramString)
  {
    this.success = false;
    try
    {
      this.scanner = new Parser.Scanner(paramString);
    }
    catch (FileNotFoundException localFileNotFoundException)
    {
      System.out.println("Unable to find file " + paramString);
      return;
    }
 
    while ((localLexeme = this.scanner.getNextLexeme()) != null)
    {
      Lexeme localLexeme;
      System.out.print("The scanner found a lexeme with source code \"" + localLexeme.getSource() + "\" at line ");
      System.out.println(localLexeme.getLineNumber() + " and assigned token " + localLexeme.getToken().name());
    }
 
    this.success = true;
  }
 
  public boolean isSuccessful()
  {
    return this.success;
  }
 
  private static class Scanner
  {
    private Scanner javaScanner;
    private Pattern pattern;
    private Matcher matcher;
    private String sourceLine;
    private int lineNumber;
 
    private Scanner()
    {
    }
 
    public Scanner(String paramString)
      throws FileNotFoundException
    {
      this.sourceLine = "";
      this.lineNumber = 0;
      this.javaScanner = new Scanner(new File(paramString));
    }
 
    public Lexeme getNextLexeme()
    {
      if (this.sourceLine.length() == 0)
      {
        if (!this.javaScanner.hasNextLine())
        {
          return null;
        }
        this.sourceLine = this.javaScanner.nextLine();
        this.lineNumber += 1;
      }
 
      this.pattern = Pattern.compile("\\s+");
      this.matcher = this.pattern.matcher(this.sourceLine);
 
      if (this.matcher.lookingAt())
      {
        this.sourceLine = this.sourceLine.substring(this.matcher.group().length());
      }
 
      for (Lexeme.Token localToken : Lexeme.Token.values())
      {
        this.pattern = Pattern.compile(localToken.getRegex());
        this.matcher = this.pattern.matcher(this.sourceLine);
 
        if (!this.matcher.lookingAt())
          continue;
        this.sourceLine = this.sourceLine.substring(this.matcher.group().length());
        return new Lexeme(this.matcher.group(), this.lineNumber, localToken);
      }
 
      return null;
    }
  }
}

and these are the errors I get:

Parser.java:30: cannot find symbol
symbol    :   variable localLexeme
location:  class Parser
            while   ((localLexeme  =  this.scanner.getNextLexeme()) !=null)
 
Parser.java:62: cannot find symbol
symbol    :    constructor Scanner(java.io.File)
location: class Parser.Scanner
               this.javaScanner = new Scanner(new File(paramString));
 
Parser.java:69: cannot find symbol
 
 
symbol    :    method hasNextLine()
location: class Parser.Scanner
                    this.sourceLine = this.javaScanner.hasNextLine();

I belive this is very easy, but i don't know why i'm not getting it!


thanx to who ever helps

Well hi d7o0om,

Im a beginner too but I think I know a bit to help you.

Your first error:
you use the variable localLexeme in a while() loop while you declare it inside the while loop, this will not work that way. The solution is simple, put the declaration before the while() loop.

Your second error:
Im not sure, haven't played with the IO yet, but try looking into the "new File(paramString)" part, try declaring it into a variable and then put it in the constructor of the Scanner(). Try debugging from there, look what type the new variable will be and it should be java.io.File else its wrong.

Your third error:
Look into the Parser.Scanner class and check if the class has the method hasNextLine(), and be specific because hasNextLine() is not the same as hasNextLine(param). The method must not have arguments.

Good luck!

Thank You so much for your help, the first tip worked very well, i don't know how i missed that.

I hope other users can help with the other problems

Thanx

You should be able too check the third error, see what methods there is.