java.lang package

[thangaprakash somasundara]

is there any built-in function to display the double/float number in two decimal digit format as 3.14752 to 3.14 ?

[Anonymous]

hi,
there is no built in fuction IMO. the best thing u can do is multiply the number by 100. then cast it to an int. and then again divide it by 100 and store the result in a double
for example to find the value of
class demo
{
public static void main(String[] args)
{
double d=2.345677;
d=d*100;
System.out.println(d);
int a=(int)d;
System.out.println(a);
d=(double)a/100;
System.out.println(d);
}
}
hope this helps
Rahul

[Milind Kulkarni]

Hi Guys,
This is how I would do it. The code is self explanatory so I am not including any details.
class Test {
static double d = 3.14752;
public static void main (String [] args) {
Double dd = new Double(d);
String s = dd.toString();
String ss = s.substring(0,4);
System.out.println (ss);
}
}
Regards,
Milind

[This message has been edited by Milind Kulkarni (edited June 07, 2000).]

[Frank Carver]

Hmm. Milind's solution works for the constant number given, but then so would <pre>System.out.println("3.14")</pre>.
To use this approach for arbitrary numbers is a little more complex, you have to allow for lots of digits before the point, less than 2 after the point, and a potential negative sign.
How about:

public class NumberFormatter 
{
  private static final int decimalPlaces = 2;
  
  public static String format(double d)
  {
    String s = "" + d;
    int point = s.indexOf('.');  // strictly should be localized
    if (point >= 0)
    {
      s = s.substring(0, Math.min(point + 1 + decimalPlaces, s.length()));
    }
    
    return s;
  }
  
  /* test code */
  
  private static void test(double d)
  {
    System.out.println("format(" + d + ") => '" + format(d) + "'");
  }
  
  public static void main(String args[])
  {
    test(3.1415927);
    test(-3.1415927);
    test(45678);
    test(-45678);
    test(3.1);
    test(3);
  }
}

All this is interesting, but a bit pointless, when there is a built-in class to do this for us anyway. Consider:

public class NumberFormatter2 
{
  private static java.text.DecimalFormat fmt = new java.text.DecimalFormat("0.00");
  public static String format(double d)
  {
    return fmt.format(d);
  }
  
  
  /* test code */
  
  private static void test(double d)
  {
    System.out.println("format(" + d + ") => '" + format(d) + "'");
  }
  
  public static void main(String args[])
  {
    test(3.1415927);
    test(-3.1415927);
    test(45678);
    test(-45678);
    test(3.1);
    test(3);
  }
}

These formatting classes were introduced to Java in version 1.1, so they should be available in your implementation.

[Milind Kulkarni]

Thanks Frank for enlightening me !!
Regards,
Milind

[Anonymous]

hi Frank,
can u tell me what are the disadvantages of my method vis-a- vis yours.

Rahul

[Frank Carver]

Well, the only advantages of your solution are that a reader can easily see what's happening, and it would work on very old (pre 1.1) versions of Java.
The advantages of using the built-in formatting system are:
1. You don't need to write it.
2. It's extremely flexible; you can control all aspects of how your number is displayed.
3. It's internationalized; It will correctly use '.' as the decimal separator in England and the USA, but ',' in Germany (for example), so you don't need to worry about that.
4. It's available to all your classes; you don't need to worry about including a version in every applet, application, servlet, jar etc.
5. Someone else is maintaining, optimizing and testing it for you.
In short, it's always better to use a built-in version of something if it does what you want.

[Anonymous]

hi,
thanks frank. i will start using u r method in my applications from now on.
Rahul