Manipulating .txt Files in Java

Problem:

To solve this assignment, you are supposed to know file input/output (reading from and writing to a file) and array list usage.

First, fill an input file called input.txt with 12 numbers: 4 6 8 3 1 2 3 9 8 4 3 0 (each integer on a line).

In your main method, read these items from the input file, fill them in an integer array list, and write them to an output file called output.txt after concatenating each of them with the corresponding index.

The content of the output file will be:            

                                                                            4 0

6 1

8 2

3 3

1 4

2 5

3 6

9 7

8 8

4 9

3 10

0 11

                Then, remove the item at index 6 from the array list and the print on the console (on the screen using System.out.println(..)) the size of that array list (which is supposed to be 11 now) on one line, the array list items on the next line, and the sum of the items on the last line.

                The printed output on the screen must be:     11

4 6 8 3 1 2 9 8 4 3 0

48

Solution:

/**-------------------ExerciseII.java---------------------------*/
import java.io.File;
import java.io.FileNotFoundException;
import java.util.ArrayList;
import java.util.Formatter;
import java.util.Scanner;

public class ExerciseII
{
 public static void main(String[] args) throws FileNotFoundException
 {
  //Calling the input.txt file with 12 numbers from memory
  Scanner scan = new Scanner(new File("input.txt"));
  
  //Creating an array list
  ArrayList  arrayList = new ArrayList();
  
  //Filling the 12 numbers in the arrayList
  while (scan.hasNext())
   arrayList.add(scan.nextInt());  
  
  //Creating output.txt file
  Formatter input = new Formatter("output.txt");
  
  //Filling the output.txt with required content
  for (int i = 0 ; i < arrayList.size(); i++)
   input.format(arrayList.get(i) + " " + i + "%n");
  
  //Closing output.txt
  input.close();
  
  //Removing item at index 6 from the array list
  arrayList.remove(6);
  
  //Printing arrayList size
  System.out.println(arrayList.size());
  
  //Printing arrayList content
  for (int i = 0 ; i < arrayList.size();i++)
   System.out.print(arrayList.get(i) + " ");
  System.out.println();
  
  //Printing sum
  int sum = 0;
  for (int i = 0 ; i < arrayList.size();i++)
   sum += arrayList.get(i);
  System.out.println(sum);
 }
}

/**-------------------input.txt---------------------------*/
4
6
8
3
1
2
3
9
8
4
3
0
/**-----------------output.txt---------------------------*/
4 0
6 1
8 2
3 3
1 4
2 5
3 6
9 7
8 8
4 9
3 10
0 11