BufferedReader error?

[Umogrim]

Hello all, I am new to this forum, and also to java, so bear with me a bit.
I got this exercise in lab class to make a program that converts from one type of temperature to the other two(eg. Celsius to farenheit and kelvin). Now, I was progressing along nicely, and managed to make the first one(for Celsius) work, however Farenheit and Kelvin converters don't work. I asked my lab helper what was wrong, and he was stumped. The IDE(netbeans 6.8) isn't showing any underlined red errors, so I hope someone here could help me.

import java.io.*;

public class Main
{

    public static void main(String[] args) throws IOException
    {
        BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Ingrese la medida de temperature que quiere convertir(1: Celsius, 2: Farenheit, 3:Kelvin): ");

        if(1==Integer.parseInt(bf.readLine()))
        {
            new BufferedReader(new InputStreamReader(System.in));
            System.out.print("Ingrese la temperatura Celsius que quiere convertir: ");
            double c=Double.parseDouble(bf.readLine());

            double kelvinC = c + 273.15;
            double farenheitC = 1.8*c + 32;

            System.out.print("La temperatura "+c+"°C es equivalente a "+farenheitC+"°F y "+kelvinC+"°K.");            
        }

        if(2==Integer.parseInt(bf.readLine()))
        {
            new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Ingrese la temperatura Farenheit que quiere convertir: ");
            double f=Double.parseDouble(bf.readLine());

            double celsiusF=(f-32)/1.8;
            double kelvinF=(f+459.67)/1.8;

            System.out.print("La temperatura "+f+"°F es equivalente a "+celsiusF+"°C y "+kelvinF+"°K.");
        }

        else if(3==Integer.parseInt(bf.readLine()))
        {
            new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Ingrese la temperatura Kelvin que quiere convertir: ");
            double k=Double.parseDouble(bf.readLine());

            double celsiusK=k-273.15;
            double farenheitK=(9/5)*k - 459.67;

            System.out.print("La temperatura "+k+"°K es equivalente a "+celsiusK+"°C y "+farenheitK+"°F");
        }
        

    }

}

When it prompts me with "Ingrese la medida de temperature que quiere convertir(1: Celsius, 2: Farenheit, 3:Kelvin): ", any answer other than 1 gives me this error:

Exception in thread "main" java.lang.NumberFormatException: For input string: ""
at java.lang.NumberFormatException.forInputString(Num berFormatException.java:48)
at java.lang.Integer.parseInt(Integer.java:470)
at java.lang.Integer.parseInt(Integer.java:499)
at laboratorio1.Main.main(Main.java:32)
Java Result: 1
BUILD SUCCESSFUL (total time: 14 seconds)

I hope someone can help me, thanks in advance.

[JosAH]

import java.io.*;

public class Main
{

    public static void main(String[] args) throws IOException
    {
        BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Ingrese la medida de temperature que quiere convertir(1: Celsius, 2: Farenheit, 3:Kelvin): ");

        if(1==Integer.parseInt(bf.readLine()))
        {
            new BufferedReader(new InputStreamReader(System.in));
            System.out.print("Ingrese la temperatura Celsius que quiere convertir: ");
            double c=Double.parseDouble(bf.readLine());

            double kelvinC = c + 273.15;
            double farenheitC = 1.8*c + 32;

            System.out.print("La temperatura "+c+"°C es equivalente a "+farenheitC+"°F y "+kelvinC+"°K.");            
        }

        if(2==Integer.parseInt(bf.readLine()))
        {
            new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Ingrese la temperatura Farenheit que quiere convertir: ");
            double f=Double.parseDouble(bf.readLine());

            double celsiusF=(f-32)/1.8;
            double kelvinF=(f+459.67)/1.8;

            System.out.print("La temperatura "+f+"°F es equivalente a "+celsiusF+"°C y "+kelvinF+"°K.");
        }

        else if(3==Integer.parseInt(bf.readLine()))
        {
            new BufferedReader(new InputStreamReader(System.in));
            System.out.println("Ingrese la temperatura Kelvin que quiere convertir: ");
            double k=Double.parseDouble(bf.readLine());

            double celsiusK=k-273.15;
            double farenheitK=(9/5)*k - 459.67;

            System.out.print("La temperatura "+k+"°K es equivalente a "+celsiusK+"°C y "+farenheitK+"°F");
        }
        

    }

}

A few corrections:

1) Delete all of these lines in your if-statements; they're useless:

            new BufferedReader(new InputStreamReader(System.in));

2) After you have read a number (by reading a line) don't read any other lines, i.e. before your three if statements do this instead:

        BufferedReader bf=new BufferedReader(new InputStreamReader(System.in));
        System.out.println("Ingrese la medida de temperature que quiere convertir(1: Celsius, 2: Farenheit, 3:Kelvin): ");

String line= bf.readLine();
int choice= Integer.parseInt(line);

... and change your ifs to this:

if (choice == 1) { ... }
else if (choice == 2) { ... }
else if (choice == 3) { ... }

kind regards,

Jos

[Umogrim]

Thanks a bunch JosAH! That did the trick. You really saved me(and my lazy partner) on this one.