Need help with a programming exercise

[ararar]

So I'm very new to java and i dont know too much but i cant figure out how to make this program work correctly. I am supposed to take a unit of measurement and that the user inputs and convert it to any of several units that they desire using if statements. this is the class i have to far

public class UnitConverter
{
 /**
  *Constructs a class that converts measurements to different units
  */
 public UnitConverter()
 {
  unitTo= null;
  unitFrom= null;
  val=0;
 }
 /**
  *Constructs a class that converts measurements to different units
  *@param inUnitFrom the unit to convert
  */
 public UnitConverter(String inUnitFrom, String inUnitTo, double inVal)
 {
  unitFrom = inUnitFrom;
  unitTo= inUnitTo;
  inVal = val;
 }
 public double getConversion()
 {
 	double finalVal=0;
 	double valInMeters=0;
  {
  if (unitFrom.equalsIgnoreCase("m"))
  valInMeters = val;
  else if (unitFrom.equalsIgnoreCase("ft"))
  valInMeters = val*M_IN_FT;
  else if (unitFrom.equalsIgnoreCase("mm"))
  valInMeters = val*M_IN_MM;
  else if (unitFrom.equalsIgnoreCase("cm"))
  valInMeters = val*M_IN_CM;
  else if (unitFrom.equalsIgnoreCase("in"))
  valInMeters = val*M_IN_IN;
  else if (unitFrom.equalsIgnoreCase("mi"))
  valInMeters = val*M_IN_MI;
  else if (unitFrom.equalsIgnoreCase("km"))
  valInMeters = val*M_IN_KM;
  else
  	valInMeters=0;
  }
  {
  	if (unitTo.equalsIgnoreCase("m"))
  	finalVal = valInMeters;
  else if (unitTo.equalsIgnoreCase("ft"))
  	finalVal = valInMeters/ M_IN_FT;
  else if (unitTo.equalsIgnoreCase("mm"))
  	finalVal = valInMeters/ M_IN_MM;
  else if (unitTo.equalsIgnoreCase("cm"))
  	finalVal = valInMeters/ M_IN_CM;
  else if (unitTo.equalsIgnoreCase("in"))
  	finalVal = valInMeters/ M_IN_IN;
  else if (unitTo.equalsIgnoreCase("mi"))
  	finalVal = valInMeters/ M_IN_MI;
  else if (unitTo.equalsIgnoreCase("km"))
  	finalVal = valInMeters/ M_IN_KM;
  	else
  		finalVal=0;
  }
  return finalVal;
 }
 private String unitTo;
 private String unitFrom;
 private double val;

 public static final double M_IN_FT = .3048;
 public static final double M_IN_MM = .001;
 public static final double M_IN_CM = .01;
 public static final double M_IN_IN = .0254;
 public static final double M_IN_MI = 1609.344;
 public static final double M_IN_KM = 1000;

}


and this is the tester
import java.util.Scanner;
public class UnitConverterTester23
{
 public static void main (String[]args)
 {
  Scanner scan = new Scanner (System.in);
  System.out.println("Converting from:");
  String from = scan.next();
  System.out.println("Converting to:");
  String to = scan.next();
  System.out.println("Enter the value of the measurement");
  double val= scan.nextInt();
  UnitConverter conv1 = new UnitConverter(from, to, val);
  UnitConverter conv2 = new UnitConverter (to, from, val);
  System.out.println(val+ " " +from+ " = " +fjfjf+ " " +to);
 }
}

any help would be greatly appreciated

[Eranga]

Lets start from the the beginning.

So if I'm correct in your application, user can define units convert from-to with the value. I've collect that information using a scanner. Fine.

But think about this. Use has to enter the unit, and sometimes them may confusing with it. So it's better to print kind of a legend that units you can handle from your application. What you think?

[ararar]

okay yes that sounds like a good idea to me

[ararar]

my problem is that everytime i go to convert it gives me 0.0 as the conversion and i do not know how to fix this. the instructions said something about defining two objects of the class that convert between meters and a given unit, but I'm not sure how to go about that

[mine0926]

Does this one compile?
How did you know that it gives you zero value as result? Because I did not see in your code that you print the result. Also, I did not see that you call getConversion() method. And what is fjfjf? Did not see its declaration.

[ararar]

yeah i was messing with the code the bottom should be

UnitConverter conv1 = new UnitConverter(from, to, val);
UnitConverter conv2 = new UnitConverter (to, from, val);
System.out.println(val+ " " +from+ " = " +conv1.getConversion()+ " " +to);
}
}
/*Output:
--------------------Configuration: 5.14 - JDK version 1.6.0_21 <Default> - <Default>--------------------
Converting from:
cm
Converting to:
mm
Enter the value of the measurement
10
10.0 cm = 0.0 mm

Process completed.*/

[mine0926]

{ public UnitConverter()
{
unitTo= null;
unitFrom= null;
val=0;
}

public UnitConverter(String inUnitFrom, String inUnitTo, double inVal)
{
unitFrom = inUnitFrom;
unitTo= inUnitTo;
inVal = val;
}

What is the use of val? You declared with a FIX value of ZERO then you passed it to inVal
which makes it ZERO also.

valInMeters = val*M_IN_FT;

Remember that val has a value of zero and you multiply it to M_IN_FT. That makes the result ZERO as always

[Eranga]

My suggestion is to step down the process. Start from one conversion at a time. Take a piece of paper and write down your design, may be in a simple flow chart. Then move to the coding. Think about the user aspects as well.

[ararar]

yeah i fixed it thanks alot

[Eranga]

You are welcome. :)

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