String to double errors

[bigvanilla]

Hi, I am trying to cut down the decimals to two, but I get this error(see picture).
I have try several methods but getting the same errors.

// Patrik

import java.text.DecimalFormat;

public class TestD
{

    public TestD(){
        
        System.out.println("Double value: " + getArea());
    }

    public double getArea() {
        
        double dTemp = Math.PI;
        
        DecimalFormat twoDForm = new DecimalFormat("#.##");
        
        String aTemp = twoDForm.format(dTemp);
        
        return Double.valueOf(aTemp.trim()).doubleValue();
    }
}

[JosAH]

I runs fine for me; sorry, that thumbnail is too small for me; what is it protesting about? Is "3.14" (with a dot) or "3,14" (with a comma).

kind regards,

Jos

[bigvanilla]

I am using BlueJ.

Here is the error:

java.lang.NumberFormatException: For input string: "3,14"
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:1224)
at java.lang.Double.valueOf(Double.java:475)
at TestD.getArea(TestD.java:30)
at TestD.<init>(TestD.java:19)
at sun.reflect.NativeConstructorAccessorImpl.newInsta nce0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInsta nce(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newI nstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Construc tor.java:513)
at bluej.runtime.ExecServer$3.run(ExecServer.java:790 )

[JosAH]

I am using BlueJ.

Here is the error:

java.lang.NumberFormatException: For input string: "3,14"
at sun.misc.FloatingDecimal.readJavaFormatString(Floa tingDecimal.java:1224)

See the comma instead of the dot? You formatter is using a locale that has a comma instead of a dot for separating the decimal expansion of the fraction; here 3,14 instead of 3.14. Check the used Locale and possibly use another one.

kind regards,

Jos

[bigvanilla]

Thanks it is solved now :-)

[bigvanilla]

More problem I need help for. This is nearly the same code with two extra variables.

import java.text.DecimalFormat;

public class TestD
{   
    int width;
    int height;

    public TestD(){
        width = 20;
        height = 30;
        
        System.out.println("Double value: " + getArea(width, height));
    }

    public double getArea(int width, int height) {
        
        double dTemp = Math.PI * (double)width * (double)height;
        
        DecimalFormat twoDForm = new DecimalFormat("#,##");
        
        String aTemp = twoDForm.format(dTemp);
        
        return Double.valueOf(aTemp.trim()).doubleValue();
    }
}

I get this error message:

[COLOR="DarkRed"]java.lang.NumberFormatException: For input string: "18 85"
	at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1224)
	at java.lang.Double.valueOf(Double.java:475)
	at TestD.getArea(TestD.java:29)
	at TestD.<init>(TestD.java:14)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
	at bluej.runtime.ExecServer$3.run(ExecServer.java:790)[/COLOR]

It is complaining on the last row of the code with the return.

Anyone who can help me with this?

[Fubarable]

In your current code, your DecimalFormat object is superfluous and doing nothing but helping to cause an error. If the method takes in two numbers and then returns a number (a double), why convert it to a String? If however your goal is to learn to use a DecimalFormat object to convert a double to a String and then back again, then you'll want to use DecimalFormat's parse method as well:

import java.text.DecimalFormat;
import java.text.ParseException;

public class TestD {
   int width;
   int height;

   public TestD() throws ParseException {
      width = 20;
      height = 30;
      System.out.println("Double value: " + getArea(width, height));
   }

   public double getArea(int width, int height) throws ParseException {
      double dTemp = Math.PI * (double) width * (double) height;
      DecimalFormat twoDForm = new DecimalFormat("#,##");
      String aTemp = twoDForm.format(dTemp);
      System.out.println("aTemp is " + aTemp);
      //!!return Double.valueOf(aTemp.trim()).doubleValue();
      return twoDForm.parse(aTemp).doubleValue();
   }
   
   public static void main(String[] args) {
      try {
         new TestD();
      } catch (ParseException e) {
         // TODO Auto-generated catch block
         e.printStackTrace();
      }
   }
}

[bigvanilla]

Hi, I did run your code and got no errors :-)

But, I am still not get the double value with two decimals. Actually I do not care if I do need to convert it to a string and then back to double.
It was just one solution I found on the net. (I do not know if this could be done different?)

The main reson is to just get a double value with only two decimals.

// Patrik

[Fubarable]

Hi, I did run your code and got no errors :-)

But, I am still not get the double value with two decimals.

The method is supposed to return a double, and doubles really don't have a number of decimals -- rather a String representation of a double does. So don't worry about the number of decimals of the number until you want to display the String.

Actually I do not care if I do need to convert it to a string and then back to double.

You should worry about this as it messes with your result for no reason at all and can introduce errors.

The main reson is to just get a double value with only two decimals.

Again, use a DecimalFormat to create a String from the double that has two decimals, but again only do this when you want to display the double as a String.

[JosAH]

I really don't understand where that space comes from in "18 85"; 20*30*PI == 1884.9555921539 which figures but I think the OP's locale is still a bit strange ...

kind regards,

Jos