Referencing one method's output in another method of same class

Question

Here is my main method code:

public class WeightCalculatorTest {
    public static void main(String[] args) {
        WeightCalculator weCa_init = new WeightCalculator(100);
        weCa_init.displayWeight();
        WeightCalculator weCa_def = new WeightCalculator();
        weCa_def.displayWeight();

        WeightCalculator weCa = new WeightCalculator(123);
        weCa.setWeight();
        weCa.displayWeight();
    }
}

Here is the method:

import java.util.Scanner;

public class WeightCalculator {

    private int weight = 0;
    private int hundreds;
    private int fifties;
    private int twenties;
    private int tens;
    private int fives;
    private int ones;
    private int total;
    private int[] result;

    // Default constructor
    public WeightCalculator()
    {

        weight=0;
        System.out.println();
    }   

    // Initial constructor
    public WeightCalculator(int w)
    {

        weight=w;
        System.out.println();
    }

    public void setWeight( ) {
           Scanner keyboard = new Scanner (System.in);
           System.out.println("Life needs a balance");
           System.out.print("How many pounds does the item weight? ");
            weight = keyboard.nextInt();
         }// end inputWeight

        public int[] calculateBalanceWeights() {

            hundreds = weight/100;
            weight %= 100; 

            fifties = weight/50;
            weight %= 50; 

            twenties = weight/20;
            weight %= 20; 

            tens = weight/10;
            weight %= 10; 

            fives = weight/5;
            ones = weight %5;   

            total = hundreds+fifties+twenties+tens+fives+ones;

            int [] result = {hundreds, fifties, twenties, tens, fives, ones, total};

            return result; 

        }// end calcDays


        public void displayWeight() {
            System.out.println("You need "+calculateBalanceWeights()[6]+" weights in total:");
            System.out.println("   "+hundreds +" 100 lbs");
            System.out.println("   "+fifties +"  50 lbs");
            System.out.println("   "+twenties +"  20 lbs");
            System.out.println("   "+tens +"  10 lbs");
            System.out.println("   "+fives +"   5 lbs");
            System.out.println("   "+ones +"   1 lbs");
        }// end of display

}// end of class Time

My question is in this part of my code:

System.out.println("You need "+calculateBalanceWeights()[6]+" weights in total:");

why if I reference total it does not work - shows 0, while other variables can be referenced by name. And if I reference for other varibales in displayWeight as calculateBalanceWeights()[0] for hundreds it does not work?

I`m really confused how return variables are stored and referenced by other methods?

Aslo from the main method I can print the result array with

System.out.print(Arrays.toString(weCa.calculateBalanceWeights()));

But the results are wrong for the number entered?

Answer 1

I didn't get the problem. I guess your program is working correctly. I ran your code and got the following.

For the following part of your code:

WeightCalculator weCa_init = new WeightCalculator(100);
weCa_init.displayWeight();

Program outputs the following.

You need 1 weights in total:
   1 100 lbs
   0  50 lbs
   0  20 lbs
   0  10 lbs
   0   5 lbs
   0   1 lbs

The result contains 1 100 lbs because of new WeightCalculator(100).

For the following part of your code:

WeightCalculator weCa_def = new WeightCalculator();
weCa_def.displayWeight();

Program outputs the following.

You need 0 weights in total:
   0 100 lbs
   0  50 lbs
   0  20 lbs
   0  10 lbs
   0   5 lbs
   0   1 lbs

This time you initialized object with no value [new WeightCalculator()]. Thats why everything is zero here.

Please note that you have two constructor, one with parameter and one without parameter.

For the following part of your code:

WeightCalculator weCa = new WeightCalculator(123);
weCa.setWeight();
weCa.displayWeight();

Program outputs the following.

Life needs a balance
How many pounds does the item weight? 373
You need 8 weights in total:
   3 100 lbs
   1  50 lbs
   1  20 lbs
   0  10 lbs
   0   5 lbs
   3   1 lbs

This time you initialized object with a value [new WeightCalculator(123)] but after calling setWeight(), program gets 373 as user input and thus provide output accordingly.

So, what is the unexpected thing happening here?

---

Update

Why if I reference total it does not work - shows 0, while other variables can be referenced by name.

You are getting zero as output when you use,

System.out.println("You need "+ total +" weights in total:");

inside displayWeight() function.

But your code works correctly when you write,

System.out.println("You need " + calculateBalanceWeights()[6] + " weights in total:");

This is obvious because a call to the function calculateBalanceWeights() updates all the variables - hundreds, fifties, twenties, tens, fives, ones and total.

When you simply use total inside displayWeight(), you are not making a call to the calculateBalanceWeights() function. As a result, no variable gets updated.

Do the following to achieve your desired behavior.

public void displayWeight() {
    calculateBalanceWeights();
    System.out.println("You need "+total+ " weights in total:");
    System.out.println("   "+hundreds +" 100 lbs");
    System.out.println("   "+fifties +"  50 lbs");
    System.out.println("   "+twenties +"  20 lbs");
    System.out.println("   "+tens +"  10 lbs");
    System.out.println("   "+fives +"   5 lbs");
    System.out.println("   "+ones +"   1 lbs");
}

This code snippet provides output correctly.

If I reference for other varibales in displayWeight as calculateBalanceWeights()[0] for hundreds it does not work!

Because you can not call calculateBalanceWeights() many times. Once you call calculateBalanceWeights(), all the parameter values (hundreds, fifties, twenties, tens, fives, ones and total) gets updated.

So, just call calculateBalanceWeights() once and save the return value in a variable and then use it for printing results.

Aslo from the main method I can print the result array with System.out.print(Arrays.toString(weCa.calculateBalanceWeights())); But the results are wrong for the number entered?

The numbers are not wrong. I checked it. For example, if user gives 373 as input,

System.out.print(Arrays.toString(weCa.calculateBalanceWeights()));

prints the following.

[3, 1, 1, 0, 0, 3, 8]

Just compare it with what you are returning from calculateBalanceWeights() as given below.

int [] result = {hundreds, fifties, twenties, tens, fives, ones, total};

Hopefully, the updated answer will sort your confusion.