Inputting numbers in java?

[Energize]

How do I input integers into a program?

This code will take the number I give it, but then it outputs the sum completley wrong.

public class gallonstolitres
{
public static void main(String[] args) throws Exception
{
char gallons;
System.out.println("how many gallons do you want to be converted?");
gallons = (char)System.in.read();
System.in.read();
System.out.println(gallons+" gallons is "+gallons*4.5+" litres");
}
}

I assume I need to change the char gallons to int gallons, otherwise it uses the int value for the keyboard char I pressed and not the actual number I typed in? How do I do this?

 

[Energize]

Everything seems more complicated in java, why didn't they just use c++'s method of typing in cin>> for any type of variable?

 

[Energize]

You need to use Integer.parseInt() to convert the character to an integer and store it in an int variable.

P.S. put your code in

 tags ;)[/QUOTE]

Where do I put this line of code in my program?

 

[Energize]

It's just that it seems to be much more typing, wouldn't it make sense to only use objects where nessecary to reduce the amount of code?

 

[Energize]

Ok this is my code now:

public class integer
{
public static void main(String[] args) throws Exception
{
int gallons;
System.out.println("Please enter the amount of gallons you want to be converted");
gallons = System.in.read();
          System.in.read();
			 int number = Integer.parseInt(gallons);
			 System.out.println(gallons+" gallons is "+number*4.5+" litres");
			 }}

But I get this error

 ----jGRASP exec: javac -g C:\java files\integer.java

integer.java:9: cannot find symbol
symbol  : method parseInt(int)
location: class java.lang.Integer
			 int number = Integer.parseInt(gallons);
			                     ^
1 error

 ----jGRASP wedge2: exit code for process is 1.
 ----jGRASP: operation complete.

 

[Energize]

Hmmm,

When I type in 5, I get "53 gallons is 238.5 litres".

 

[Energize]

Ok, now I have this;

public class integer
{
public static void main(String[] args) throws Exception
{
int gallons;
System.out.println("Please enter the amount of gallons you want to be converted");
gallons = System.in.read();
          System.in.read();
			 System.out.println(String.valueOf(gallons)+" gallons is "+ String.valueOf(gallons*4.5)+" litres");
			 }}

But I still get 5 = 53 = 238.5

 

[Energize]

I'm doing java because its the only programming course my school do, but I have to ask, why would you want to use java instead of c++ or c# when making a program for a windows pc? Java programs do seem to run slow.

 

[Energize]

Ok this works,

import javax.swing.*;
 
public class galtolit
{
   public static void main(String[] args)
   {
      String i;
      int gallons;
      i = JOptionPane.showInputDialog("Enter the number of gallons you want to be converted");
      gallons = Integer.parseInt(i);
      System.out.println(gallons+" gallons is "+gallons*4.6+" litres");
      System.exit(0);
   }
}

but when I try to get rid of the graphics, it doesn't.

public class galtolit
{
   public static void main(String[] args) throws Exception
   {
      String i;
      int gallons;
      i = (String) System.in.read("Enter the number of gallons you want to be converted");
		System.in.read();
      gallons = Integer.parseInt(i);
      System.out.println(gallons+" gallons is "+gallons*4.6+" litres");
      System.exit(0);
   }
}

Instead I get "ConvertString.java:8: cannot find symbol
symbol : method read(java.lang.String)
location: class java.io.InputStream
i = (String) System.in.read("Enter the number of gallons you want to be converted");
........................... ^"

I suppose I can live with using the graphics box, but it's more stuff to remember.

 

[Energize]

Presumably because System.in.read() doesn't take in any arguments - you're giving it a String.

And why are you calling in.read twice?

Guide, says I need to put it in again to catch the user pressing enter.