Thread: Using methods improperly

I just recently started to learn about methods. I'm not that good with them nor do I fully understand them. This program I am writing is a simple program its asks the user if they want to convert pounds to kilograms or kilograms to pounds. In this assignment we are required to have 4 methods: The main method, P2k(pounds to kilos method), K2P, and a method that prints the results. I am not sure how to properly call the methods into the main method Here is my code if anyone can help me out.

 
 
package weightconversion;
 
import java.util.Scanner;
 
/**
 *
 * @author Zach
 */
public class WeightConversion {
 
    //Create global conversion rate
    public static final double CONVERSION_RATE =2.204;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       //Declare variables
        int nChoice=0;             //the user will choose pounds or kilos.
        Scanner input = new Scanner (System.in);     //Used to read input
        double dP2K=0;                //Converted pounds to kilos
        double  dK2P=0;               //Converted kilos to pounds
        double  dPounds=0;            //variable for pounds
        double  dKilos=0;             //variable for kilos
        double  dWeight=0;            //Weight variable
        double  dConvertedWeight=0;   //variable for weight converted
 
 
        //Display weight conversion
        System.out.println("WEIGHT CONVERSION");
        //Displays pounds to kilos
        System.out.println("1." + "Pounds to kilograms");
        //Displays kilos to pounds
        System.out.println("2." + "Kilograms to pounds");
 
        //Prompt user to select type of conversion
        System.out.print("Please select the type of conversion"
                + " you would like to make:");
        //Record input
        nChoice = input.nextInt();
 
        //Prompt user to enter pounds
            if (nChoice == 1) {
                //Prompt user to enter pounds
                System.out.print("Please enter the pounds:");
                //Record input
                dPounds = input.nextDouble();
                //Calls method P2k with parameter dPounds
                dConvertedWeight = P2K(dPounds);
            }
            else if (nChoice == 2){
                //Promp user to enter kilos
                System.out.print("Please enter the kilograms:");
                //Record input
                dKilos = input.nextDouble();
                //Calls method K2P with parameter dKilos
                dConvertedWeight = K2P (dKilos);
            }
            //What happens if user incorrectly enters wrong integer
            else 
         //Tell user they need to run program again
         System.out.println("Error: Invalid conversion selection," + 
                 "Please run the program again. " );
            dWeight = dPounds + dWeight;
            dWeight = dKilos + dWeight;
    }
 
             //Converts pounds to kilograms   
            public static double P2K(double dPounds){
            double dConvertedPounds = 0;         //The converted pounds
            dConvertedPounds = dPounds/CONVERSION_RATE;  //Formula
            return dConvertedPounds;           //Retrun statement
            }
 
         public static double K2P(double dKilos){
             double dConvertedKilos = 0;           //The converted kilos
             dConvertedKilos = dKilos/CONVERSION_RATE;   //Formula
             return dConvertedKilos;      //Return statement
 
         }
         public static void PrintResults(dConvertedWeight,nChoice,dWeight){
 
         }
 
 
 
 
 
 
    }

Im getting an error code for the last method saying it can not find the symbol, I know i'm doing it incorrectly, but not sure how to properly write it.

public static void PrintResults(dConvertedWeight,nChoice,dWeight){

}


You forgot to put the variable types.

i.e.


public static void PrintResults(double dConvertedWeight, int nChoice, double dWeight)


Also, as for how to properly call a method inside the main method, you've already done it correctly here:

dConvertedWeight = P2K(dPounds);

dConvertedWeight = K2P (dKilos);

So i have the conversions working but I think im doing it without calling the printresults method could anyone tell me how i would incorporate the printresults method into my calculations, also when is displays it has to say 50 pounds but it says 50.0 pounds, should i change it to an int?

 
 
*/
package weightconversion;
 
import java.util.Scanner;
 
/**
 *
 * @author Zach
 */
public class WeightConversion {
 
    //Create global conversion rate
    public static final double CONVERSION_RATE =2.204;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       //Declare variables
        int nChoice=0;             //the user will choose pounds or kilos.
        Scanner input = new Scanner (System.in);     //Used to read input
        double dP2K=0;                //Converted pounds to kilos
        double  dK2P=0;               //Converted kilos to pounds
        double  dPounds=0;            //variable for pounds
        double  dKilos=0;             //variable for kilos
        double  dWeight=0;            //Weight variable
        double  dConvertedWeight=0;   //variable for weight converted
 
 
        //Display weight conversion
        System.out.println("WEIGHT CONVERSION");
        //Displays pounds to kilos
        System.out.println("1." + "Pounds to kilograms");
        //Displays kilos to pounds
        System.out.println("2." + "Kilograms to pounds");
 
        //Prompt user to select type of conversion
        System.out.print("Please select the type of conversion"
                + " you would like to make:");
        //Record input
        nChoice = input.nextInt();
 
        //Prompt user to enter pounds
            if (nChoice == 1) {
                //Prompt user to enter pounds
                System.out.print("Please enter the pounds:");
                //Record input
                dPounds = input.nextDouble();
                //Calls method P2k with parameter dPounds
                dConvertedWeight = P2K(dPounds);
                //Display calculation
                System.out.print(dPounds +   " pounds is " +   dConvertedWeight 
                        + " kilograms." );
            }
            else if (nChoice == 2){
                //Promp user to enter kilos
                System.out.print("Please enter the kilograms:");
                //Record input
                dKilos = input.nextDouble();
                //Calls method K2P with parameter dKilos
                dConvertedWeight = K2P (dKilos);
                //Display calculation
                System.out.print(dKilos + "kilograms is " + dConvertedWeight 
                        + " pounds. ");
            }
            //What happens if user incorrectly enters wrong integer
            else 
         //Tell user they need to run program again
         System.out.println("Error: Invalid conversion selection," + 
                 "Please run the program again. " );
            dWeight = dPounds + dWeight;
            dWeight = dKilos + dWeight;
 
            if (nChoice == 1){
 
            }
    }
 
             //Converts pounds to kilograms   
            public static double P2K(double dPounds){
            double dConvertedPounds = 0;         //The converted pounds
            dConvertedPounds = dPounds/CONVERSION_RATE;  //Formula
            return dConvertedPounds;           //Retrun statement
            }
 
         public static double K2P(double dKilos){
             double dConvertedKilos = 0;           //The converted kilos
             dConvertedKilos = dKilos*CONVERSION_RATE;   //Formula
             return dConvertedKilos;      //Return statement
 
         }
         public static void PrintResults(double dConvertedWeight,int nChoice,
                 double dWeight){
 
         }
 
 
 
 
 
 
    }

Here are the results

WEIGHT CONVERSION
1.Pounds to kilograms
2.Kilograms to pounds
Please select the type of conversion you would like to make:1
Please enter the pounds:50
50.0 pounds is 22.686025408348456 kilograms.BUILD SUCCESSFUL (total time: 6 seconds)



Kilos to pounds :WEIGHT CONVERSION
1.Pounds to kilograms
2.Kilograms to pounds
Please select the type of conversion you would like to make:2
Please enter the kilograms:50
50.0kilograms is 110.2 pounds. BUILD SUCCESSFUL (total time: 3 seconds)


and the last one choosing neither :
WEIGHT CONVERSION
1.Pounds to kilograms
2.Kilograms to pounds
Please select the type of conversion you would like to make:-1
Error: Invalid conversion selection,Please run the program again.
BUILD SUCCESSFUL (total time: 2 seconds)

Okay so I moved it to the print method and called that method, but I messed up somehow because now when I convert something I says 0.0 pounds and does the conversion and repeats it twice.

 
 * and open the template in the editor.
 */
package weightconversion;
 
import java.util.Scanner;
 
/**
 * This method converts kilograms to pounds or pounds to kilograms
 * @author Zach
 * @version 10/4/2013
 */
public class WeightConversion {
    // This method prompts user to either select pounds or kilograms and then input a number which returns a conversion rate
 
    //Create global conversion rate
    public static final double CONVERSION_RATE =2.204;
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
       //Declare variables
        int nChoice=0;             //the user will choose pounds or kilos.
        Scanner input = new Scanner (System.in);     //Used to read input
        double dP2K=0;                //Converted pounds to kilos
        double  dK2P=0;               //Converted kilos to pounds
        double  dPounds=0;            //variable for pounds
        double  dKilos=0;             //variable for kilos
        double  dWeight=0;            //Weight variable
        double  dConvertedWeight=0;   //variable for weight converted
 
 
        //Display weight conversion
        System.out.println("WEIGHT CONVERSION");
        //Displays pounds to kilos
        System.out.println("1." + "Pounds to kilograms");
        //Displays kilos to pounds
        System.out.println("2." + "Kilograms to pounds");
 
        //Prompt user to select type of conversion
        System.out.print("Please select the type of conversion"
                + " you would like to make:");
        //Record input
        nChoice = input.nextInt();
 
        //Prompt user to enter pounds
            if (nChoice == 1) {
                //Prompt user to enter pounds
                System.out.print("Please enter the pounds:");
                //Record input
                dPounds = input.nextDouble();
                //Calls method P2k with parameter dPounds
                dConvertedWeight = P2K(dPounds);
                //Calls method to print results
                PrintResults(dConvertedWeight,nChoice,dWeight);
 
            }
            else if (nChoice == 2){
                //Promp user to enter kilos
                System.out.print("Please enter the kilograms:");
                //Record input
                dKilos = input.nextDouble();
                //Calls method K2P with parameter dKilos
                dConvertedWeight = K2P (dKilos);
                 //Calls method to print results
                PrintResults(dConvertedWeight,nChoice,dWeight);
 
            }
            //What happens if user incorrectly enters wrong integer
            else 
         //Tell user they need to run program again
         System.out.println("Error: Invalid conversion selection," + 
                 "Please run the program again. " );
            dWeight = dPounds + dWeight;
            dWeight = dKilos + dWeight;
 
            if (nChoice == 1){
 
            }
    }
 
             //Converts pounds to kilograms   
            public static double P2K(double dPounds){
            double dConvertedPounds = 0;         //The converted pounds
            dConvertedPounds = dPounds/CONVERSION_RATE;  //Formula
            return dConvertedPounds;           //Retrun statement
            }
 
         public static double K2P(double dKilos){
             double dConvertedKilos = 0;           //The converted kilos
             dConvertedKilos = dKilos*CONVERSION_RATE;   //Formula
             return dConvertedKilos;      //Return statement
 
         }
         public static void PrintResults(double dConvertedWeight,int nChoice,
                 double dWeight){
             double dKilos=dWeight;
             double dPounds =dWeight;
              //Display calculation
                System.out.print(dPounds +   " pounds is " +   dConvertedWeight 
                        + " kilograms." );
                //Display calculation
                 //Display calculation
                System.out.print(dKilos + "kilograms is " + dConvertedWeight 
                        + " pounds. ");
 
 
         } // end Method weightConversion
 
 
 
 
 
 
    } // end Class WeightConversion

These are the results :
WEIGHT CONVERSION
1.Pounds to kilograms
2.Kilograms to pounds
Please select the type of conversion you would like to make:1
Please enter the pounds:50
0.0 pounds is 22.686025408348456 kilograms.0.0kilograms is 22.686025408348456 pounds. BUILD SUCCESSFUL (total time: 3 seconds)

Kilos to pounds:
WEIGHT CONVERSION
1.Pounds to kilograms
2.Kilograms to pounds
Please select the type of conversion you would like to make:2
Please enter the kilograms:50
0.0 pounds is 110.2 kilograms.0.0kilograms is 110.2 pounds. BUILD SUCCESSFUL (total time: 3 seconds)