Wrapper

[Henas Cirtak]

I'm trying to convert a String to a double value. My book says to first create a Double object and then convert the Double to a double value. It's not working... anybody got any ideas?

Thanks!


import java.applet.*;
import java.awt.*;
import java.awt.event.*;

public class CalcPay extends Applet implements ActionListener
{
TextField text1 = new TextField("hours worked",15);
TextField text2 = new TextField("hourly rate", 15);
Button button = new Button("Press Me");
Label label = new Label(" ");

public void init()
{
add(text1);
add(text2);
add(button);
add(label);
button.addActionListener(this);
invalidate();
validate();
}

public void actionPerformed(ActionEvent e)
{
String text1Number = text1.getText();
String text2Number = text2.getText();

Double text1Double = Double.valueOf(text1Number);
Double text2Double = Double.valueOf(text2Number);

double text1double = doubleValue(text1Double);
double text2double = doubleValue(text2Double);

}
}

[Henas Cirtak]

This is the error that I get...

C:\Documents and Settings\Patrick\My Documents\Java Programs\Chapter 6\CalcPay\CalcPay.java:31: cannot resolve symbol
symbol : method doubleValue (java.lang.Double)
location: class CalcPay
double text1double = doubleValue(text1Double);
^
C:\Documents and Settings\Patrick\My Documents\Java Programs\Chapter 6\CalcPay\CalcPay.java:32: cannot resolve symbol
symbol : method doubleValue (java.lang.Double)
location: class CalcPay
double text2double = doubleValue(text2Double);
^
2 errors

Tool completed with exit code 1

[Sonny Gill]

Originally posted by Henas Cirtak:

double text1double = doubleValue(text1Double);
double text2double = doubleValue(text2Double);

Have you defined the doubleValue() method somewhere else that you are calling?
If you havent, then perhaps what you wanted to do was call the doubleValue method defined in java.lang.Double class.

Also have a look at parseDouble method defined in the same class.

cheers.
Sonny

[Henas Cirtak]

How do I call the java.lang.Double class? I thought that it was automatically imported.

[Joyce Lee]

Hi Henas,

How do I call the java.lang.Double class? I thought that it was automatically imported.

Yes. java.lang package is automatically imported. So you don't have to import it.

  
public void actionPerformed(ActionEvent e) {
    String text1Number = text1.getText();
    String text2Number = text2.getText();
 
    Double text1Double = Double.valueOf(text1Number);
    Double text2Double = Double.valueOf(text2Number);
 
[B]
    // corrected version
    double text1double = text1Double.doubleValue();
    double text2double = text2Double.doubleValue();
[/B]
}

Better version...

public void actionPerformed(ActionEvent e) {
    String text1Number = text1.getText();
    String text2Number = text2.getText();
 
[B]
    double text1double = Double.parseDouble(text1Number);
    double text2double = Double.parseDouble(text2Number);
[/B]
}

Joyce
[ October 13, 2004: Message edited by: Joyce Lee ]

[Henas Cirtak]

Thank you I got it to work! Although, my book gives the example...

String stringValue = new String("147.82");
Double tempValue = Double.valueOf(stringValue);
double doubleValue = doubleValue(tempValue);

Am I just missing what the book is trying to teach or is it wrong?

[Joyce Lee]

Am I just missing what the book is trying to teach or is it wrong?
It could be a typo error. You might want to check out the book's errata.

Joyce

[Sonny Gill]

or perhaps the example in your book defines a method doubleValue somewhere else, could be something like -

double doubleValue(Double d){ return d.doubleValue();}

[Dun Dagda]

Hi,
unless the doubleValue method is defined somewhere else, I suggest the code given in your textbook example is a typo. It probably should read something like:

String stringValue = new String("147.82");
Double tempValue = Double.valueOf(stringValue);
double doubleValue = tempValue.doubleValue();

where you use the valueOf method to return a Double object, tempValue, then you call its doubleValue() method to return a double primitive.
However the examples already posted above by others using the static parseDouble(String s) method would probably work more efficiently.
Happy Coding!
Dun Dagda