Thread: Double rounding

Hi .. I would like to round off a number in a method and return the rounded number. I tried many different ways but I always got the same error message:

Matematik.java:70: error: incompatible types
return df.format(volym);
^
required: double
found: String
1 error

import java.text.DecimalFormat;
 
	public static double volume (int r, int h)
	{
	DecimalFormat df = new DecimalFormat("#.##");
 
	double volym=PI*r*r*h;
	return df.format(volym);
	}

Your DecimalFormat object returns a String object. Use the Double class to parse the String and return a double value.

I´m not sure if I did right but I did like this:

	public static double volume (int r, int h)
	{
	DecimalFormat df = new DecimalFormat("#.##");
	double volym=PI*r*r*h;
	return Double.valueOf(df.format(volym));
	}

and got the error message like this:

--------------------Configuration: <Default>--------------------
Klotets volym är: 113,04

Cylinderns volym är: Exception in thread "main" java.lang.NumberFormatException: For input string: "28,26"
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:1241)
at java.lang.Double.valueOf(Double.java:504)
at Matematik.volume(Matematik.java:69)
at Matematik.main(Matematik.java:39)

Process completed.

Do you know maybe what I did wrong? :/

For some odd reason it's returning a comma rather than the period. Try using this as your format "###.##"

Not too sure why it is returning a comma there though.

What is your value for PI? Also, the data type. I just tested this code and it works just fine. My only guess now is that your PI variable is set wrong :/

public static double volume (int r, int h)
{
	DecimalFormat df = new DecimalFormat("#.##");
 
	double volym=3.14*r*r*h;
return Double.parseDouble(df.format(volym));
}

I defined PI like this: public static final double PI = 3.14;

It´s very strange. I made a simple program and copied your code, but I got the same fail.

import java.text.DecimalFormat;
 
public class Matte {
 
public static void main (String[] args)
{
 
int r=3;
int h=5;
 
 System.out.print(volume(r,h));
}
 
 
public static double volume (int r, int h)
{
	DecimalFormat df = new DecimalFormat("#.##");
 
	double volym=3.14*r*r*h;
return Double.parseDouble(df.format(volym));
}
}

Hello krillov!
I tried your code and it gives me the same error. It's probably what Norm says in post#5. A "sloppy" way to fix this is by replacing the "," with a "." to the String which is returned by the DecimalFormat format method and then parse it to a double. The String class has methods for that.
Hope this helps.

Thanks, it worked. I tried in a smaller program like this:

import java.text.DecimalFormat;
 
public class Matte {
 
	public static final double PI = 3.14;
 
public static void main (String[] args)
{
 
int r=3;
int h=7;
 
 System.out.print(volume(r,h));
}
 
 
public static double volume (int r, int h)
{
	DecimalFormat df = new DecimalFormat("#.##");
 
	double volym=PI*r*r*h;
	String volym2=df.format(volym);
	volym2=(replace1(volym2));
	return Double.parseDouble(volym2);
}
 
 
public static String replace1(String volym2)
{
 	return volym2.replaceAll("," , ".");
}
}