CODEWITHSUNDEEP
javaoopobjectmultidimensional-array
Baroness Sledjoys
Baroness Sledjoys

Reputation: 121

Logic Error with Summing Up Columns [Java]

This is very similar to this post except that the code is now part of an object instead of a method.

Again, this is how it should look:

Enter 3 rows and 4 columns:

1 2 3 4
5 6 7 8
9 10 11.2 12.5

You entered:

1.0 2.0 3.0 4.0
5.0 6.0 7.0 8.0
9.0 10.0 11.2 12.5

The sums are:

15.0 18.0 21.2 24.5

This is my code:

else if (choice == 2) {

    // Prompt user
    System.out.println("You Selected Sum Columns");

    // Enter array values
    double[][] myList = new double[3][4];
    double[][] userList = new double[3][4];

    feature2 f2 = new feature2();

    f2.run(myList, input);

    f2.getInput(userList);

}

and

import java.util.Scanner;

public class feature2 {

    public void run(double[][] myList,Scanner input) {


        // 2D arrays are like spreadsheets ROW and Columns
        System.out.println("Enter " + myList.length + " rows and " + myList[0].length + " columns: ");
        for (int i = 0; i < myList.length; i++){
          for (int j = 0; j < myList[0].length; j++){
              myList[i][j] = input.nextDouble();
          }
        }

    }

    public void getInput(double[][] userList) {



        System.out.println("You Entered:");
        for (int i = 0; i < userList.length; i++) {
            for (int j = 0; j < userList[0].length; j++) {

                // chars are just ints!
                System.out.print(userList[i][j] + " ");
            }

            // every row
            System.out.print("\n");
        }

        System.out.println("\n The sums are:");

        for (int column = 0; column < userList[0].length; column++) {
              double total = 0.0;

              for (int row = 0; row < userList.length; row++){
                  // sum column
                  total += userList[row][column];
              }

              System.out.print(total + " ");
        }

        // space for formating
         System.out.print("\n");
    }
}

This is what happens instead:

Enter 1 Random 2D Chars 
Enter 2 Sum Columns
Enter 3 Identical Arrays
Any other input will exit2
You Selected Sum Columns
Enter 3 rows and 4 columns: 
1 2 3 4
5 6 7 8
9.1 10.2 11.3 12.9
You Entered:
0.0 0.0 0.0 0.0 
0.0 0.0 0.0 0.0 
0.0 0.0 0.0 0.0 

 The sums are:
0.0 0.0 0.0 0.0

Now I have the opposite problem of the last post. Everything formats correctly, but it doesn't calculate properly. This is my only problem with the entire code.

Upvotes: 1

Views: 39

Answers (2)

JB Nizet
JB Nizet

Reputation: 691635

You're asking the user to fill an array, and then displaying that array. So you need only one array, right?

Yet you have two arrays in your code: myList, which is filled by the user, and userList, which is displayed.

double[][] myList = new double[3][4];
double[][] userList = new double[3][4];

feature2 f2 = new feature2();

// ask the user to fill myList
f2.run(myList, input);

// but display userList
f2.getInput(userList);

Note that your naming is very confusing. The method which gets the input from the user is named run(), and the user which displays the array is named... getInput().

Upvotes: 2

Misa Lazovic
Misa Lazovic

Reputation: 2823

Well, you are first instantiating 2 empty arrays, then writing to one array and finally reading from second one (which is empty - actually filled with default double values, which is 0.0).
Basically, instead of:

double[][] myList = new double[3][4];
double[][] userList = new double[3][4];

feature2 f2 = new feature2();

f2.run(myList, input);

f2.getInput(userList);

try with:

double[][] myList = new double[3][4];

feature2 f2 = new feature2();

f2.run(myList, input);

f2.getInput(myList);

Upvotes: 2

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