Question

This is java. I need help with my computer science class.

Question 11

Assume that you have an array of integers named arr. The following program segment is intended to sum arr [0]through arr[n−1], where n = arr.length:
         sum = 0;
         i = 0;
         n = arr.length;
         while (i != n)
         {
            i++;
            sum += arr[i];
         }

In order for this segment to perform as intended, which of the following modifications, if any, should be made?

1.No modification is necessary

2. sum = 0; i = 0; should be changed to sum = arr[1]; i = 1;

3. while (i != n) should be changed to while (i <= n)

4. sum += arr[i]; should be changed to sum += arr[i+1];

5. i++; should be interchanged with sum += arr[i];

Question 13

Assume arr2 is declared as a two-dimensional array of integers. Which of the following segments of code successfully calculates the sum of all elements arr2?

1. int sum = 0;
   for(int j = 0; j < arr2.length; j++)
   {
      for(int k = 0; k < arr2[j].length; k++)
      {
         sum += arr2[k][j];
      }
   }
2. int sum = 0;
   for(int j = arr2.length − 1; j >= 0; j−−)
   {
      for(int k = 0; k < arr2[j].length; k++)
      {
         sum += arr2[j][k];
      }
   }
3. int sum = 0;
   for(int[] m : arr2)
   {
      for(int n : m)
      {
         sum += n;
      }
   }

1. I only

2. II only

3. I and II only

4. II and III only

5. I and III only.

Question 18

When must the method myMethod be invoked using dot notation?

1. When myMethod is private.

2. When myMethod is invoked by a method in the same class as myMethod.

3. When myMethod is public.

4. When myMethod is both private and static.

5. When myMethod is invoked by a method in a different class than myMethod.

Answer 1

11.

• 5th option is the correct option.
• In while loop, i is incremented first and then sum = arr[1] and then each time i is incremented and sum becomes a[1]+a[2]+a[3]...a[n-1].
• So, if we interchange the line such that i is incremented later so, sum = arr[0] in the first iteration and then i becomes =1 and then add all the values till i=n-1.

13.

• 4rth option is correct.
• Ist part will fail in case if there is an uneven matrix where a number of rows and columns are equal.
• 2nd part will take one row at a time and add each element of a column. For j=0, k=0,1,2 all the columns are added. In the next iteration, j=1, k=0,1,2, and all the column value for row 1 will be added and in the third iteration, j=2, k=0,1,2, and all the column value for row 3 will be added.
• 3rd part will also compute sum as it will take one row at a time and then take each element of the row and add the values.

18.

• The fifth option is correct.
• Other classes can invoke the function written in different classes using the dot notation.
• Option 1 is incorrect as private methods are not invoked outside the class and inside the class, we don't need dot notation.
• Option 2 is incorrect as in the same class, we can call directly by function name.
• Option 3 is incorrect if the method is public it can be accessed throughout.
• Option 4 is incorrect as the private methods are not accessed outside the class and static methods are always called by the static functions only.

Friend, this was a really nice question to answer. If you find my answer helpful, please like it. Thanks.