Question

1. This lab has 2 classes: TwoDArray.java and Lab11.java. Lab11.java is already given to you. Do not make any changes to this file. The only file you are expected to write for this lab is TwoDArray.java 2. Open Lab11.java and understand the code by tracing it line by line. There are some new things we have not seen before. Let us examine them now. 1. In this lab we will be using a text file for input. Whenever we do input/output using text files, we need to import java.io.*; import this package 2. public static void main(String args[]) throws IOException Whenever we open a file for reading some things could potentially go wrong. For example: • The input file may not exist . The input file may have access restrictions . The input file may not be in the correct format . File may be residing in a remote server and a connection could not be established When you open a file for writing, the following things could go wrong: • The disk may be write protected . The disk may be full The above mentioned issues could cause an IOException. At the end of the semester, we will cover exceptions, but for now, just think of exceptions as something outside he normal mode of execution. Whenever your code could cause an exception, we need to either deal with it or inform the compiler that your code could potentially cause an exception. Since we have not yet covered how to deal with an exception, we are telling the compiler that our code could cause an IOException in the method header. That is what throws IOException in the main method header means. Only methods could throw exceptions not classes.

This is the contents of Lab11.java

import java.util.Scanner;
import java.io.*;

public class Lab11
{
public static void main(String args[]) throws IOException {
Scanner inFile = new Scanner(new File(args[0]));
Scanner keyboard = new Scanner(System.in);
  
TwoDArray array = new TwoDArray(inFile);
inFile.close();
int numRows = array.getNumRows();
int numCols = array.getNumCols();
int choice;
  
do {
System.out.println();
System.out.println("\t1. Find the number of rows in the 2D array");
System.out.println("\t2. Find the number of columns in the 2D array");
System.out.println("\t3. Find the sum of elements in a particular row");
System.out.println("\t4. Find the sum of elements in a particular column");
System.out.println("\t5. Find the sum of all elements along the border");
System.out.println("\t6. Find the sum of elements in the top left to bottom right diagonal");
System.out.println("\t7. Find the sum of elements in the top right to bottom left diagonal");
System.out.println("\t8. Print the array on the screen");
System.out.println("\t9. Quit the program");

System.out.print("\nYour selection: ");
choice = Integer.parseInt(keyboard.nextLine() );

switch(choice) {
case 1:
System.out.println("There are " + array.getNumRows() + " rows in the array");
break;

case 2:
System.out.println("There are " + array.getNumCols() + " columns in the array");
break;

case 3:
System.out.print("Enter the row number. It should be between 1 and " + numRows + ": ");
int rowNum = Integer.parseInt(keyboard.nextLine() );
if (rowNum >= 1 && rowNum <= numRows) {
System.out.println("The sum of elements in row " + rowNum + " is " +
array.rowSum(rowNum - 1));
}
else {
System.out.println("The row number you entered " + rowNum + " is invalid");
}
break;

case 4:
System.out.print("Enter the column number. It should be between 1 and " + numCols + ": ");
int colNum = Integer.parseInt(keyboard.nextLine() );
if (colNum >= 1 && colNum <= numCols) {
System.out.println("The sum of elements in column " + colNum + " is " +
array.columnSum(colNum - 1));
}
else {
System.out.println("The column number you entered " + colNum + " is invalid");
}
break;

case 5:
System.out.println("The sum of all the elements along the border is " +
array.borderSum() );
break;

case 6:
if (numRows != numCols) {
System.out.println("The 2D array is not a square. Diagonal is not well defined");
}
else {
System.out.println("The sum of elements in the top left to bottom right diagonal is "+
array.topLeftToBottomRightDiagonalSum() );
}
break;

case 7:
if (numRows != numCols) {
System.out.println("The 2D array is not a square. Diagonal is not well defined");
}
else {
System.out.println("The sum of elements in the top right to bottom left diagonal is "+
array.topRightToBottomLeftDiagonalSum() );
}
break;

case 8:
System.out.println(array);
break;

case 9:
System.out.println("Thanks for using my program. Good bye!");
break;

default:
System.out.println("Illegal Choice. Try again");
} // end of switch
} while (choice != 9);
} // main method   
}

Please help me, Thank you!

Answer 1

// Java code for above problem

import java.util.Scanner;
import java.io.*;

class TwoDArray
{
   int rows=0,cols=0;
   int twoDArray[][];
   TwoDArray(Scanner inFile)
   {
       rows=inFile.nextInt();
       cols=inFile.nextInt();
       twoDArray=new int[rows][cols];
       for(int i=0;i<rows;i++)
       {
           for(int j=0;j<cols;j++)
           {
               twoDArray[i][j]=inFile.nextInt();
           }
       }
   }
   public int getNumRows()
   {
       return this.rows;
   }
   public int getNumCols()
   {
       return this.cols;
   }
   public int rowSum(int rowNum)
   {
       int sum=0;
       for(int j=0;j<cols;j++)
           sum+=twoDArray[rowNum][j];
       return sum;
   }
   public int columnSum(int colNum)
   {
       int sum=0;
       for(int i=0;i<rows;i++)
           sum+=twoDArray[i][colNum];
       return sum;
   }
   public int borderSum()
   {
       int sum=0;
       for(int j=0;j<cols;j++)
           sum+=twoDArray[0][j]+twoDArray[rows-1][j];
       for(int i=0;i<rows;i++)
           sum+=twoDArray[i][0]+twoDArray[i][cols-1];
       sum=sum-twoDArray[0][0]-twoDArray[rows-1][0]-twoDArray[0][cols-1]-twoDArray[rows-1][cols-1];
       return sum;
   }
   public int topLeftToBottomRightDiagonalSum()
   {
       int sum=0;
       for(int i=0;i<rows;i++)
           sum+=twoDArray[i][i];
       return sum;
   }
   public int topRightToBottomLeftDiagonalSum()
   {
       int sum=0;
       for(int i=rows-1;i>=0;i--)
           sum+=twoDArray[i][i];
       return sum;
   }
   public String toString()
   {
       String array="";
       for(int i=0;i<rows;i++)
       {
           for(int j=0;j<cols;j++)
           {
               array+=String.valueOf(twoDArray[i][j])+" ";
           }
           array+="\n";
       }
       return array;
   }
}

public class Lab11
{
   public static void main(String args[]) throws IOException
   {
       Scanner inFile = new Scanner(new File(args[0]));
       Scanner keyboard = new Scanner(System.in);
      
       TwoDArray array = new TwoDArray(inFile);
       inFile.close();
       int numRows = array.getNumRows();
       int numCols = array.getNumCols();
       int choice;
      
       do
       {
           System.out.println();
           System.out.println("\t1. Find the number of rows in the 2D array");
           System.out.println("\t2. Find the number of columns in the 2D array");
           System.out.println("\t3. Find the sum of elements in a particular row");
           System.out.println("\t4. Find the sum of elements in a particular column");
           System.out.println("\t5. Find the sum of all elements along the border");
           System.out.println("\t6. Find the sum of elements in the top left to bottom right diagonal");
           System.out.println("\t7. Find the sum of elements in the top right to bottom left diagonal");
           System.out.println("\t8. Print the array on the screen");
           System.out.println("\t9. Quit the program");

           System.out.print("\nYour selection: ");
           choice = Integer.parseInt(keyboard.nextLine() );

           switch(choice)
           {
               case 1:
                   System.out.println("There are " + array.getNumRows() + " rows in the array");
                   break;

               case 2:
                   System.out.println("There are " + array.getNumCols() + " columns in the array");
                   break;

               case 3:
                   System.out.print("Enter the row number. It should be between 1 and " + numRows + ": ");
                   int rowNum = Integer.parseInt(keyboard.nextLine() );
                   if (rowNum >= 1 && rowNum <= numRows)
                   {
                       System.out.println("The sum of elements in row " + rowNum + " is " +
                       array.rowSum(rowNum - 1));
                   }
                   else
                   {
                       System.out.println("The row number you entered " + rowNum + " is invalid");
                   }
                   break;

               case 4:
                   System.out.print("Enter the column number. It should be between 1 and " + numCols + ": ");
                   int colNum = Integer.parseInt(keyboard.nextLine() );
                   if (colNum >= 1 && colNum <= numCols)
                   {
                       System.out.println("The sum of elements in column " + colNum + " is " +
                       array.columnSum(colNum - 1));
                   }
                   else
                   {
                       System.out.println("The column number you entered " + colNum + " is invalid");
                   }
                   break;

               case 5:
                   System.out.println("The sum of all the elements along the border is " + array.borderSum() );
                   break;

               case 6:
                   if (numRows != numCols)
                   {
                       System.out.println("The 2D array is not a square. Diagonal is not well defined");
                   }
                   else
                   {
                       System.out.println("The sum of elements in the top left to bottom right diagonal is "+
                       array.topLeftToBottomRightDiagonalSum() );
                   }
                   break;

               case 7:
                   if (numRows != numCols)
                   {
                       System.out.println("The 2D array is not a square. Diagonal is not well defined");
                   }
                   else
                   {
                       System.out.println("The sum of elements in the top right to bottom left diagonal is "+
                       array.topRightToBottomLeftDiagonalSum() );
                   }
                   break;

               case 8:
                   System.out.println(array);
                   break;

               case 9:
                   System.out.println("Thanks for using my program. Good bye!");
                   break;

               default:
                   System.out.println("Illegal Choice. Try again");
           } // end of switch
       } while (choice != 9);
   } // main method
}

Sample output:

Let the filename be "inputs.txt" and it has following data:

4

4

1 2 3 4

5 6 7 8

9 10 11 12

13 14 15 16

then the output is as follows:

1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 1 There are 4 rows in the array 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 2 There are 4 columns in the array

1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 3 Enter the row number. It should be between 1 and 4: 4 The sum of elements in row 4 is 58 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal, 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 5 The sum of all the elements along the border is 102 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program

Your selection: 4 Enter the column number. It should be between 1 and 4: 2, The sum of elements in column 2 is 32 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 6 The sum of elements in the top left to bottom right diagonal is 34, 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 7 The sum of elements in the top right to bottom left diagonal is 34

1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal, 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 9 Thanks for using my program. Good bye!

// Mention in comments if any mistakes or errors are found. Thank you.

1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 1 There are 4 rows in the array 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 2 There are 4 columns in the array

1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 3 Enter the row number. It should be between 1 and 4: 4 The sum of elements in row 4 is 58 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal, 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 5 The sum of all the elements along the border is 102 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program

Your selection: 4 Enter the column number. It should be between 1 and 4: 2, The sum of elements in column 2 is 32 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 6 The sum of elements in the top left to bottom right diagonal is 34, 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 7 The sum of elements in the top right to bottom left diagonal is 34

1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal, 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 8 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1. Find the number of rows in the 2D array 2. Find the number of columns in the 2D array 3. Find the sum of elements in a particular row 4. Find the sum of elements in a particular column 5. Find the sum of all elements along the border 6. Find the sum of elements in the top left to bottom right diagonal 7. Find the sum of elements in the top right to bottom left diagonal 8. Print the array on the screen 9. Quit the program Your selection: 9 Thanks for using my program. Good bye!