Question

Write a Java program that uses printf, and takes user input to find the name of the File.

1. FileCompare (20)

Write a program that compares to files line by line, and counts the number of lines that are different. You can use file1.txt and file2.txt when testing your program, but you must ask for the file names in the input.

main

Interactively requests the names of the two files, after creating the Scanner for the keyboard.

Creates a Scanner for each of the two files.

Calls countDifferentLines with references to the two Scanners as parameters and accepts an integer return value.

Prints the result (see sample).

countDifferentLines

Accepts references to the two Scanners as parameters

Compares the two files line by line – They may have a different number of lines

Return the number of lines that are different

Sample output

Please enter name of the first file to compare: file1.txt

Please enter name of the second file to compare: file2.txt

The files differ in 4 line(s)

Answer 1

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

public class FileCompare {
   public static void main(String[] args) throws Exception {
       Scanner sc = new Scanner(System.in);
       //reading file names
       System.out.println("Enter name of the first file to compare: ");
       String f1 = sc.next();
       System.out.println("Enter name of the second file to compare: ");
       String f2 = sc.next();

       int c=countDifferentLines(new Scanner(new File(f1)), new Scanner(new File(f2)));
       System.out.println("The files differ in "+c+" line(s)");
   }

   private static int countDifferentLines(Scanner sc1, Scanner sc2) throws Exception {
       int count = 0;
       String l1 = "", l2 = "";
       //looping the files
       while (sc1.hasNext() || sc2.hasNext()) {
           //reading lines
           if(sc1.hasNext())
           l1 = sc1.nextLine();
           if(sc2.hasNext())
           l2 = sc2.nextLine();
           //checking the difference
           if (l1 == null && l2 == null)
               return count;
           if (l1 == null && l2 != null)
               count++;
           else if (l1 != null && l2 == null)
               count++;
           else if (!l1.equals(l2))
               count++;

       }
       //returns count
       return count;
   }
}

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