Java Question..
- Thread starter MillerMan
- Start date
You can't use instanceof for primitives. Something like this will work, I think:
There is, no doubt, a better way to do it (maybe with autoboxing).
Code:
boolean is_dbl;
try
{
Double tmp = new Double(tempInput.doubleValue());
is_dbl = true;
}
catch(NumberFormatException e)
{
System.out.println("Not double.");
is_dbl = false;
}There is, no doubt, a better way to do it (maybe with autoboxing).
Last edited by a moderator:
arjan de lumens
Veteran
Java is a statically typed language, and 'double' is not a class (which is why 'instanceof' doesn't work). If you have declared 'tempInput' as a 'double', then it will always be a 'double', and if you have declared it as anything else than a 'double', then it will never be a 'double'.
If you have inputted a string and want to check whether the string is representable as a double, then try something like
boolean canBeRepresentedAsDouble( string S )
{
try { Double.valueOf( S ); }
catch (NumberFormatException e) { return false; }
return true;
}
If you have inputted a string and want to check whether the string is representable as a double, then try something like
boolean canBeRepresentedAsDouble( string S )
{
try { Double.valueOf( S ); }
catch (NumberFormatException e) { return false; }
return true;
}
Blazkowicz
Legend
double post.
Last edited by a moderator:
Blazkowicz
Legend
this seems dangerous to me, if N == -1 
(be it a double or a signed int)
what comes to my mind :
if (n==(int)n) // n is a integer
if (n==(double)n) // n is a double
absolutely no guarantees ^^
(be it a double or a signed int)what comes to my mind :
if (n==(int)n) // n is a integer
if (n==(double)n) // n is a double
absolutely no guarantees ^^
Here my code..... It converts celisus to fahreheit and vise versa
.. Just a little revision project...
import java.util.*;
public class TempReader
{
/**
Computes tempreture in fahrenheit from the celisus tempreture.
@param c tempreture in celisus
@return the tempreture in fahrenheit
*/
public static double celisusToFahrenheit(double c)
{
return((c-32)/9)*5;
}
/**
Computes tempreture in celisus from the fahrenheit tempreture.
@param f tempreture in fahrenheit
@return the tempreture in celisus
*/
public static double fahrenheitToCelisus(double f)
{
return((f*9)/5)+32;
}
public static void main(String[] args)
{
double tempInput;
double cel;
double fah;
String typeInput;
try
{
System.out.println("Hello, Please Enter A Tempreature");
Scanner intKeyboard = new Scanner(System.in);
tempInput = intKeyboard.nextDouble();
if(!(tempInput instanceof Double));
{
throw new InputMismatchException("Error: A Type Other Than A Number Has Been Inputed!");
}
System.out.println("Is The Tempreture In Fahrenheit (f) Or Celsius (c) ?");
Scanner stringKeyboard = new Scanner(System.in);
typeInput = stringKeyboard.nextLine();
if(!(typeInput instanceof String));
{
throw new InputMismatchException("Error: A Type Other Than A String Has Been Inputed!");
}
if(typeInput.trim().toLowerCase().equals("c"))
{
fah = fahrenheitToCelisus(tempInput);
System.out.println("Your Tempreture In Fahrenheit Is: "+fah);
}
else if(typeInput.trim().toLowerCase().equals("f"))
{
cel = celisusToFahrenheit(tempInput);
System.out.println("Your Tempreture In Celsius Is: "+cel);
}
else
{
System.out.println("Error: You Can Only Enter \'C\' Or \'c\' For Celsius Or \'F\' Or \'f\' For Fahrenhiet");
}
}
catch(InputMismatchException e)
{
System.out.println(e.getMessage());
System.out.println("Invaild Type Entered!");
}
}
}
.. Just a little revision project...
import java.util.*;
public class TempReader
{
/**
Computes tempreture in fahrenheit from the celisus tempreture.
@param c tempreture in celisus
@return the tempreture in fahrenheit
*/
public static double celisusToFahrenheit(double c)
{
return((c-32)/9)*5;
}
/**
Computes tempreture in celisus from the fahrenheit tempreture.
@param f tempreture in fahrenheit
@return the tempreture in celisus
*/
public static double fahrenheitToCelisus(double f)
{
return((f*9)/5)+32;
}
public static void main(String[] args)
{
double tempInput;
double cel;
double fah;
String typeInput;
try
{
System.out.println("Hello, Please Enter A Tempreature");
Scanner intKeyboard = new Scanner(System.in);
tempInput = intKeyboard.nextDouble();
if(!(tempInput instanceof Double));
{
throw new InputMismatchException("Error: A Type Other Than A Number Has Been Inputed!");
}
System.out.println("Is The Tempreture In Fahrenheit (f) Or Celsius (c) ?");
Scanner stringKeyboard = new Scanner(System.in);
typeInput = stringKeyboard.nextLine();
if(!(typeInput instanceof String));
{
throw new InputMismatchException("Error: A Type Other Than A String Has Been Inputed!");
}
if(typeInput.trim().toLowerCase().equals("c"))
{
fah = fahrenheitToCelisus(tempInput);
System.out.println("Your Tempreture In Fahrenheit Is: "+fah);
}
else if(typeInput.trim().toLowerCase().equals("f"))
{
cel = celisusToFahrenheit(tempInput);
System.out.println("Your Tempreture In Celsius Is: "+cel);
}
else
{
System.out.println("Error: You Can Only Enter \'C\' Or \'c\' For Celsius Or \'F\' Or \'f\' For Fahrenhiet");
}
}
catch(InputMismatchException e)
{
System.out.println(e.getMessage());
System.out.println("Invaild Type Entered!");
}
}
}
TrueBlazkowicz_ said:this seems dangerous to me, if N == -1
, but that depends on the specifics of what he's doing. But if that's a potential possibility, something extra like if(N<0) N=-N (or if N can't be changed another if clause checking 1/(N-1)).Similar threads
