Organizing Java files and other practicalities - JavaTech: An Introduction to Scientific and Technical Computing with Java - page 154

places should be up to three, padded with blanks if the fraction needs less than
three places.
An exponential pattern appends “E0 „ to the right side. So “0.000E0 „
results in three decimal places in the significand and then an exponent, such
as “1.234E10 „ . See the Java 2 API specifications for DecimalFormat to find
the complete set of formatting pattern symbols.
The recipe for formatting a floating-point value goes as follows. First specify
a string pattern such as
String fmt =" 0.00# " ;
Then create an instance of the DecimalFormat class with this pattern:
DecimalFormat df = new DecimalFormat (fmt);
Invoke the format() method to create a formatted string:
double q = 10.0/4.0;
String str = df.format (q);
System.out.println ("q ="+ str);
In this case the resulting string is:
q = 2.50
The DecimalFormat object can be reused for new format patterns by invok-
ing the applyPattern (String format) method. The following snippet
from the program DecimalFormatDemo illustrates several format patterns for
floating-point output:
... code segment in DecimalFormatDemo ...
double q = 1.0/3.0;
// Define the format pattern in a string
String fmt =" 0.000 " ;
// Create a DecimalFormat instance for this format
DecimalFormat df = new DecimalFormat (fmt);
// Create a string from the double according to the
// format
valStr = df.format (q);
System.out.println ("1.0/3.0 ="+ valStr);
// Can change the format pattern:
df.applyPattern ("0.00000");