Calculate Distance Traveled (using Methods)

Hey guys - I need some help...

I'm trying to create a program that calculates Distance Traveled using user-input for their Speed and Time. However, the assignment requires that I write a separate method for the computation of the Distance and another to DisplayData, so I can recall it back in the Main method, then display the results in another method. But - I keep getting some errors. Any help will surely be appreciated. Thanks in advance.

Here's the Errors I'm getting from the compiler:

DistTravel.java:25: error: variable speed might not have been initialized
displayData(speed, time);
^
DistTravel.java:25: error: variable time might not have been initialized
displayData(speed, time);
^
2 errors


P.S. Bare with me on my coding. I am an amateur at Java Programming. Still learning.

Code:

---


import javax.swing.JOptionPane;
import java.io.*;

public class DistTravel
{
        public static void main(String[] args) throws IOException
        {       
                // Declare the variables.
                String input;
                int speed, time;
                       
                // The 'Distance Traveled' equation.
                Distance();
               
                // Display Data
                displayData(speed, time);
               
                System.exit(0);
        }
       
        public static int Distance()
        {       
                // Get the vehicle speed from the user.
               
                // Declare the variables
                int speed;
                int time;
               
                String input;        // To hold user's input.
               
                input = JOptionPane.showInputDialog("What is your vehicle's speed in miles-per-hours? ");
               
                // Convert the input to a double.
                speed = Integer.parseInt(input);
               
          while (speed <= 0)
                        {
                                input = JOptionPane.showInputDialog("Your speed must be greater than zero. Please re-enter. ");
                               
                                speed = Integer.parseInt(input);
                        }
               
                // Get the hours traveled from the user.
                input = JOptionPane.showInputDialog("How many hours have you traveled, thus far? ");
               
                        time = Integer.parseInt(input);
               
          while (time <= 1)
                {
                                input = JOptionPane.showInputDialog("How many hours have you traveled for? ");
                       
                                time = Integer.parseInt(input);
                }
                               
                return speed * time;
        }
       
        public static void displayData(int speed, int time)
        {               
                for(int i = 1; i <= time; i++)
                        {
                        JOptionPane.showMessageDialog(null, "Hour(s): Distance Traveled" +
                        "----------------------------" + "Hour" + ": " + i + (speed * i) + " miles traveled");
                        }
        }
}

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The error messages tell you what is wrong ie:

variable speed might not have been initialized: means the variable called 'speed' is being used before you have definitely assigned a value to it - remember class and instance variable are given default values when they are declared but local variables are not.