Parsing the input part I.

Objectives

1. Using string methods parse the input line.

Notes

• We would like to break the input line into different component parts.
• There are many different ways to do this.
  • But most of them use techniques we don't know.
  • And you need to learn this method as well.
• I am going to use the string methods
  • int indexOf(int ch)
  • String substring(int beginIndex).
• I will
  • Search the input line variable for a ','
  • If I find one, I will split the string there
    • return the first part from the function
    • Store the rest back into the input line variable.
• To do this
  • I will promote the line variable to a class variable.
  • Build a value returning function.
• Value returning functions return a value!
  • Part of the declaration is the type of value they return.
  • This replaces the void
• We can then perform an assignment by calling that function.
  • If I call my function SplitLine

  • firstOfLine = SplitLine();
            

• The last line of a value returning function should be return somevar where somevar is of the type the function returns.

• import java.io.*;
  import java.util.Scanner;
  
  public class SalesOfCoffee{
       // the next three variables are related to the scanner.
       private static final String FILE_NAME = "coffee.csv";
       private static Scanner myScanner;
       // indicate if the scanner is valid or not.
       private static boolean validScanner = false;
  
       // so I can parse the input.
       private static String line;
  
       public static void main(String[] args){
           int totalLines = 0;
           String firstOfLine;
  
           MakeScanner();
           if (!validScanner) {
               System.out.printf("Scanner not constructed\n");
               return;
           }
  
           // skip the titles.
           myScanner.nextLine();
  
           while(myScanner.hasNextLine()) {
               line = myScanner.nextLine();
               totalLines++;
  
               System.out.printf("Got '%s'\n", line);
  
               int i= 0;
  
               while (i < 8) {
  
                    firstOfLine = SplitLine();
                    System.out.printf("Back in main, firstOfLine is '%s'\n", firstOfLine);
                    ++i;
               }
               System.out.printf("The rest of the line is is '%s'\n\n\n", line);
  
  
           }
  
           System.out.printf("The file contains %d lines.\n",totalLines);
  
           myScanner.close();
       }
  
      private static void MakeScanner() {
             try {
                    myScanner = new Scanner(new File(FILE_NAME));
                    validScanner = true;
             } catch (FileNotFoundException e) {
                    System.out.printf("Cound not open %s", FILE_NAME);
             }
      }
  
      private static String SplitLine() {
           String firstPart = "";
           int position = 0;
  
           position = line.indexOf(',');
           //System.out.printf("fond a , at %d\n", position);
  
  
           if (position != -1) {
               firstPart = line.substring(0, position);
               //System.out.printf("The frist part is '%s'\n", firstPart);
               line = line.substring(position+1);
               //System.out.printf("The line is now  '%s'\n",line);
           }
  
           return firstPart;
      }
  
  }