Task 2, Cleaning up the code with a method.

Objectives

1. Use a method to clean up our code.

Notes

• Methods let us move code out of the main.
  • We can build small chunks of code that are easy to understand.
  • There we can reuse code with methods.
  • And we can make our code cleaner.
  • You will need to understand methods.
• I will mess this up, function = method = routine.
• For now, we will transfer data via Class variables.
  • Later we will use parameters to do this as well.
  • But let's grow into it.
• For now all methods will be private static
  • We may discuss that later, or that might be next semester when you discuss classes for real.
• For now, we will
  1. Declare the class variables needed for a method at the top.
  2. Declare the method below main.
  3. Use the method in main.
• Flow of control:
  • Control is transferred to a method when the method is called or invoked.
  • Code in the method is executed until the method is exited.
  • Control is returned to the calling routine when the method exits.
• To clean up the code, I am going to build a MakeScanner method
  • It will be public static void
  • It will use the class variables validScanner and myScanner.
  • Note the CammelCase for the function name.
  • I will use validScanner to indicate the scanner is valid.
  • I will call MakeScanner from the main routine.
• What we are doing is called code refactoring.

• 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;
       
       public static void main(String[] args){
           
           String line;
           int totalLines = 0;
        
           MakeScanner();
           if (!validScanner) {
               System.out.printf("Scanner not constructed\n");
               return;
           }
          
           myScanner.nextLine();
          
           while(myScanner.hasNextLine()) {
               line = myScanner.nextLine();
               totalLines++;
               
               System.out.printf("Got '%s'\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);
             }
      }
  }