Question

Lab 19 - History of Computer Science, A File IO Lab

FIRST PART OF CODING LAB:

Step 0 - Getting Starting

In this program, we have two classes, FileIO.java and FileReader.java. FileIO.java will be our “driver” program or the main program that will bring the file reading and analysis together. FileReader.java will create the methods we use in FileIO.java to simply read in our file.

Main in FileIO

For this lab, main() is provided for you in FileIO.java and contains two method calls. One line calls readFile() in the FileIO class with the name of the input file "brief\_history\_of\_cs.txt". This method then calls other methods in both the FileIO and FileReader classes. The next line calls writeFileStats() with the name of the output file "output.txt". The method writes data to the output file in a certain format and uses values from the FileIO class array fileStats.

Here’s a sneak peak at what "brief\_history\_of\_cs.txt" contains…

A Brief History of Computer Science - World Science Festival

2700-2300 B.C. The Sumerian Abacus first appeared.
87 B.C. The Antikythera mechanism, the earliest known analog computer is developed in ancient Greece.
1703 A.D. German mathematician Gottfried Wilhelm Liebnitz introduces the binary number system.
1837 Charles Babbage invents the Analytical Engine.
1843 Ada Lovelace develops the first computer algorithm.
1936 Alan Turing invents the Turing Machine.
1941 Konrad Zuse invents Z3, the first programmable digital computer.
1947 The transistor is invented at Bell Labs.
...

Uncomment the provided lines after readFile() and writeFileStats() have been written.

FileReader.java

We will first need to read in our file before we perform any analysis, so let’s start with the methods in FileReader.java. The method signatures in the FileReader class are written for you. The purpose of the class is to process a file. We have one class variable that is a Scanner object called fileScanner which we will use to read the file.

Step 1 - beginScanning()

This method will initialize our class scanner fileScanner to read from the file we were given.

Try-catch

To do this, you will want to write a try-catch block with the catch just Exception e (you may want to google this to see how to use a try-catch if you are unfamiliar).

File and Scanner

Inside this try-catch block, you will want to create a file object with the fileName as your parameter. You will then want to use this file variable for your scanner. To do this, assign fileScanner to a new scanner with the file variable that you just create as the parameter of the scanner.

Below is an example of how you can create a file and a scanner to read that file…

// Creating File instance to reference text file
File text = new File("C:/temp/test.txt");
// Creating Scanner instance to read File
Scanner scnr = new Scanner(text);

Throwing out irrelevant data

After you have initialized your class variable fileScanner in your try catch, you will need to immediately “throw out” the first line of the file. The first line of the file is just a header that is the title of the file, A Brief History of Computer Science - World Science Festival. We throw it out because it doesn’t actually hold any data for our statistical analysis.

To “throw out” the first line of the file, you will just need to simply read the next line of the scanner. Don’t store it in any variable, just call .nextLine().

Step 1 - hasMoreLines()

This method will simply check to see if there is more to read from the file.

To do this, we will check to see if our class scanner is not equal to null and can still read the next line. If this is true, then we will return true, otherwise false we will just return false.

Hint: use the scanner method .hasNextLine()

Step 2 - getNextLine()

The method will simply return the next line of the file as a string.

To do this, you will use your class scanner variable fileScanner and use the appropriate scanner method to get the next line in the file.

FILEREADER.JAVA:

import java.util.Scanner;
import java.io.File;
import java.io.IOException;

public class FileReader {
   private static Scanner fileScanner;
  
   /**
   * This method, called beginScanning, is public, static and has one parameter, a String
   * representing the name of the input file.
   *
   * Write a try-catch block in order to first create a File object, and then
   * create a Scanner for the File object. Use the Scanner to read the first
   * line of the file but do nothing with that line, as the header line in
   * the file should not contribute to the statistics.
   *
   * @param fileName A String; from readFile() of the FileIO class.
   */
   public static void beginScanning(String fileName) {
       // Student TODO

       // end Student TODO
   }
  
   /**
   * This is a public, static method called hasMoreLines which returns a boolean. This method
   * should return true as long as the FileReader class Scanner object is not
   * null and the Scanner object has additional lines in the input file to read.
   *
   * @return A boolean; to readFile() in class FileIO.
   */
   public static boolean hasMoreLines() {
       // Student TODO
      
       return false;
       // end Student TODO
   }
  
   /**
   * This is a public, static method called getNextLine which returns a String. This String
   * represents one line from the input file.
   *
   * Use the FileReader class Scanner object to read one line and return the
   * result.
   *
   * @return A String; to readFile() in FileIO.
   */
   public static String getNextLine() {
       // Student TODO
  
return "";
       // end Student TODO
   }
}

Answer 1

class FileReader {
private static Scanner fileScanner;

/**
* This method, called beginScanning, is public, static and has one parameter, a
* String representing the name of the input file.
*
* Write a try-catch block in order to first create a File object, and then
* create a Scanner for the File object. Use the Scanner to read the first line
* of the file but do nothing with that line, as the header line in the file
* should not contribute to the statistics.
*
* @param fileName A String; from readFile() of the FileIO class.
*/
public static void beginScanning(String fileName) {
try {
fileScanner = new Scanner(new File(fileName));
fileScanner.nextLine();
} catch (FileNotFoundException e) {
e.printStackTrace();
}
}

/**
* This is a public, static method called hasMoreLines which returns a boolean.
* This method should return true as long as the FileReader class Scanner object
* is not null and the Scanner object has additional lines in the input file to
* read.
*
* @return A boolean; to readFile() in class FileIO.
*/
public static boolean hasMoreLines() {
return fileScanner != null && fileScanner.hasNextLine();
}

/**
* This is a public, static method called getNextLine which returns a String.
* This String represents one line from the input file.
*
* Use the FileReader class Scanner object to read one line and return the
* result.
*
* @return A String; to readFile() in FileIO.
*/
public static String getNextLine() {
if (fileScanner != null) {
return fileScanner.nextLine();
}

return "";
}
}

******************

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