File/Scanner simple parsing issues

Question

Given a File and a Scanner object,

File simpleFile = ranFi.getSelectedFile();
Scanner text = new Scanner(simpleFile);

and these two commonplace statements:

    while(text.hasNext())
    {
        String currentLine = text.nextLine();

I'm trying to use Scanner/String class logical statements in a single if-statement clause which reads first line of file under a given matching regular expressions, such as:

String fp100 = "[S][:][A-Ze0-1]";
String fp200 = "[S][:][A-Z0-1][A-Z0-1]";
//other regexes…

and then invoke the appropriate Scanner/String class methods in same if-statement clause to read to second and onward/acceptable lines. I've read javadoc up and down but haven't figured out yet. Using currentLine.matches(regex) and text.nextLine().matches(regex), this code compiled,

    if(currentLine.matches(fp100)||currentLine.matches(fp200)||
       currentLine.matches(fp300) && text.nextLine().matches(fp100)||
       text.nextLine().matches(fp101) || text.nextLine().matches(fp200)||
       text.nextLine().matches(fp201) || text.nextLine().matches(fp300)||
       text.nextLine().matches(fp301))
    {

but throws an No Such Element Exception immediately. What am I doing wrong? Thank you in advance for your time. EDIT: I've included the stack trace, but removed the source code since this is project related.

Answer 1

I see two problems:

1. When you perform the if condition, text.nextLine() may not be available.

2. if you mean to say, execute the if when any of the currentLine Matches + any of the nextLine match as true then wrap || arguments in a brace as:

   if((currentLine.matches(fp100)||currentLine.matches(fp200)||
      currentLine.matches(fp300)) && 
      (text.nextLine().matches(fp100)||
       text.nextLine().matches(fp101) || text.nextLine().matches(fp200)||
       text.nextLine().matches(fp201) || text.nextLine().matches(fp300)||
       text.nextLine().matches(fp301)))
   

I think you wanted to write your while loop something like this:

        while(text.hasNextLine()){
           String currentLine = text.nextLine();
           String nextLine = "";
           if(text.hasNextLine())[
               nextLine  = text.nextLine();
           }

           /**ACC conditions*/
           if((currentLine.matches(fp100)||currentLine.matches(fp200)
                || currentLine.matches(fp300)) 
                && (nextLine.matches(fp100)|| nextLine.matches(fp101) 
                     || nextLine.matches(fp200)
                     || nextLine.matches(fp201) || nextLine.matches(fp300)
                     || nextLine.matches(fp301)) {
                                //current line is OK
                                System.out.println(currentLine);
                                output.write(currentLine);
                                output.write("\n");
                                abc1List.add(currentLine);
                                lineOK++;               

                                //next line is OK
                                System.out.println(nextLine);
                                output.write(nextLine);
                                output.write("\n");
                                abc1List.add(nextLine);
                                // <-- not sure if you want OK as 1 or 2 here 
                                lineOK++;           
           } /**REJ conditions*/
           else if(!currentLine.matches(fp100)||!currentLine.matches(fp101)||
                  !currentLine.matches(fp200)||!currentLine.matches(fp201)||
                  !currentLine.matches(fp300)||!currentLine.matches(fp301)){   
                        System.out.println("invalid cfg; terminating....");
                   System.exit(0);
           }
       }//end of while

Answer 2

Your while loop should start with while(text.hasNextLine()) if you are using text.nextLine().matches(regex) inside the loop. Be careful. If text.hasNext() evaluates to true, it doesn't mean that text.nextLine() will be non-null.