Java- Populate 2D Array Using For Loop and User Input

Question

I have been stuck on this code all weekend and I just need a pointer as to what I am missing. This is a school assignment so I do not want the answer I just want to know what I am doing wrong. I need to create a 2D Array that stores all user values of Fahrenheit that have been entered plus their conversions to celsius and kelvin. My Array will store the value but then clear it on the next iteration. Here is my relevant code and my most recent attempt:

   for (int i = 0; i <= 10; i++){
  //call method to show the main menu
  showMenu();

  System.out.print("Enter your selection: ");
     mySelection = keyboard.nextInt();

//switch statement to pick menu option selected. 
 switch(mySelection){

//calculate celcius
case 1: System.out.print("Please enter a Farenheit value: ");
enteredF = keyboard.nextInt();
showCelcius(enteredF);
popArray(enteredF, i);
break;

//calculate kelvin
case 2: System.out.print("Please enter a Farenheit value: ");
enteredF = keyboard.nextInt();
showKelvin(enteredF);
popArray(enteredF, i);
break;

It calls this portion that I am having an issue with:

public static float[][] popArray(float userValue, int i){
 float[][] dataHolder = new float[3][10];

  dataHolder[0][i] = userValue;
  dataHolder [1][i] = showCelcius(userValue);
  dataHolder [2][i] = (float)showKelvin(userValue);
  System.out.println("Farenheit: " + Arrays.toString(dataHolder[0]));
 System.out.println("Celcius: " + Arrays.toString(dataHolder[1]));
 System.out.println("Kelvin: " + Arrays.toString(dataHolder[2])); 

return dataHolder;

I need it to store all values in the array but it keeps clearing the previous entry. For example entering values of 0,25, and 10 give me:

For 0 entered:

Fahrenheit: [0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Celsius: [-17.777779, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Kelvin: [255.37222, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

For 25 entered:

Fahrenheit: [0.0, 25.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Celsius: [0.0, -3.8888888, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Kelvin: [0.0, 269.2611, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

For 10 entered:

Fahrenheit: [0.0, 0.0, 10.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Celsius: [0.0, 0.0, -12.222222, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
Kelvin: [0.0, 0.0, 260.92776, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

I would like my output to be:

 Fahrenheit: [0.0, 25.0, 10.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
 Celsius: [-17.777779, -3.8888888, -12.222222, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]
 Kelvin: [255.37222, 269.2611, 260.92776, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0]

Why does my array clear every time? I haven't been able to figure it out.

Move `float[][] dataHolder = new float[3][10];` to be a field, not a local variable — Scary Wombat, Oct 16 '18 at 01:49
I will try that thank you. Just curious why does that make a big difference? — Daniella, Oct 16 '18 at 01:52
Because everytime you call `popArray` it gets re-initialized. — Scary Wombat, Oct 16 '18 at 01:56
I cannot believe it took me an entire weekend for something so obvious. Do I need a constructor as well to initialize it? — Daniella, Oct 16 '18 at 01:59
If it is always going to be [3][10], then you can just declare as I posted. — Scary Wombat, Oct 16 '18 at 02:03
Okay thank you. I get an error: non-static method popArray(float,int) cannot be referenced from a static context. My methods are static though? — Daniella, Oct 16 '18 at 02:10
Did you make `dataHolder` static? Although I think you should not have your methods static — Scary Wombat, Oct 16 '18 at 02:13
I did not have it static but that did fix it! Thank you so much! I do have all my methods static I did not think that was a bad thing. — Daniella, Oct 16 '18 at 02:17
see https://stackoverflow.com/questions/2671496/java-when-to-use-static-methods — Scary Wombat, Oct 16 '18 at 02:23

Java- Populate 2D Array Using For Loop and User Input

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