Formatters and Java Print Streams

Floating-point conversions can be applied to all floating-point types: float and double, the type-wrapper classesFloatandDouble, andjava.math.BigDecimal. These conversions are:

%f
   A regular base-10 decimal number, such as 3.141593

%e
   A decimal number in scientific notation with a
   lowercase e, such as 3.141593e+00

%E
   A decimal number in scientific notation with an
   uppercase E, such as 3.141593E+00

%g
   A decimal number formatted in either regular or
   scientific notation, depending on its size and
   precision, with a lowercase e if scientific notation is
   used

%G
   A decimal number formatted in either regular or
   scientific notation, depending on its size and
   precision, with an uppercase E if scientific notation is
   used

%a
   A lowercase hexadecimal floating-point number, such
  as 0x1.921fb54442d18p1

%A
   An uppercase hexadecimal floating-point number,
   such as 0X1.921FB54442D18P1

Surprisingly, you cannot use these conversions on integer types such asintorBigDecimal. Java will not automatically promote the integer type to a floating-point type when formatting. If you try to use them, it throws anIllegalFormatConversionException.

Example 7-2 prints π in all of these formats.

Example 7-2.  Floating-point format specifiers

public class FloatingPointFormatExample {

  public static void main(String[] args){
    System.out.printf("Decimal:      %f\n", Math.PI);
    System.out.printf("Scientific notation: %e\n", Math.PI);
    System.out.printf("Scientific notation: %E\n", Math.PI);
    System.out.printf("Decimal/Scientific: %g\n", Math.PI);
    System.out.printf("Decimal/Scientific: %G\n", Math.PI);
    System.out.printf("Lowercase Hexadecimal: %a\n", Math.PI);
    System.out.printf("Uppercase Hexadecimal: %A\n", Math.PI);
  }
}

Here’s the output:

  Decimal:               3.141593
  Scientific notation:   3.141593e+00
  Scientific notation:   3.141593E+00
  Decimal/Scientific:    3.14159
  Decimal/Scientific:    3.14159
  Lowercase Hexadecimal: 0x1.921fb54442d18p1
  Uppercase Hexadecimal: 0X1.921FB54442D18P1

Please check back next week for the conclusion to this article.