Package org.apache.commons.text.numbers

Enum DoubleFormat

java.lang.Object
java.lang.Enum<DoubleFormat>
org.apache.commons.text.numbers.DoubleFormat
All Implemented Interfaces:
Serializable, Comparable<DoubleFormat>
public enum DoubleFormat extends Enum<DoubleFormat>
Enum containing standard double format types with methods to produce configured formatter instances. This type is intended to provide a quick and convenient way to create lightweight, thread-safe double format functions for common format types using a builder pattern. Output can be localized by passing a DecimalFormatSymbols instance to the formatSymbols method or by directly calling the various other builder configuration methods, such as digits.

Comparison with DecimalFormat

This type provides some of the same functionality as Java's own DecimalFormat. However, unlike DecimalFormat, the format functions produced by this type are lightweight and thread-safe, making them much easier to work with in multi-threaded environments. They also provide performance comparable to, and in many cases faster than, DecimalFormat.

It should be noted that the output String is created by formatting the output of Double.toString(). This limits the output precision to the precision required to exactly represent the input double and is dependent on the JDK implementation of Double.toString(). A number formatted with the maximum precision should be parsed to the same input double. This implementation cannot extend the String to the required length to represent the exact decimal value of the double as per BigDecimal#toString().

Examples

 // construct a formatter equivalent to Double.toString()
 DoubleFunction<String> fmt = DoubleFormat.MIXED.builder().build();

 // construct a formatter equivalent to Double.toString() but using
 // format symbols for a specific locale
 DoubleFunction<String> fmt = DoubleFormat.MIXED.builder()
      .formatSymbols(DecimalFormatSymbols.getInstance(locale))
      .build();

 // construct a formatter equivalent to the DecimalFormat pattern "0.0##"
 DoubleFunction<String> fmt = DoubleFormat.PLAIN.builder()
      .minDecimalExponent(-3)
      .build();

 // construct a formatter equivalent to the DecimalFormat pattern "#,##0.0##",
 // where whole number groups of thousands are separated
 DoubleFunction<String> fmt = DoubleFormat.PLAIN.builder()
      .minDecimalExponent(-3)
      .groupThousands(true)
      .build();

 // construct a formatter equivalent to the DecimalFormat pattern "0.0##E0"
 DoubleFunction<String> fmt = DoubleFormat.SCIENTIFIC.builder()
      .maxPrecision(4)
      .alwaysIncludeExponent(true)
      .build()

 // construct a formatter equivalent to the DecimalFormat pattern "##0.0##E0",
 // i.e. "engineering format"
 DoubleFunction<String> fmt = DoubleFormat.ENGINEERING.builder()
      .maxPrecision(6)
      .alwaysIncludeExponent(true)
      .build()

Implementation Notes

Half-even rounding is used in cases where the decimal value must be rounded in order to meet the configuration requirements of the formatter instance.

Since:
1.10.0

  • Enum Constant Details

    • PLAIN

      public static final DoubleFormat PLAIN
      Number format without exponents.

      For example: 

       0.0
 12.401
 100000.0
 1450000000.0
 0.0000000000123

    • SCIENTIFIC

      public static final DoubleFormat SCIENTIFIC
      Number format that uses exponents and contains a single digit to the left of the decimal point.

      For example: 

       0.0
 1.2401E1
 1.0E5
 1.45E9
 1.23E-11

    • ENGINEERING

      public static final DoubleFormat ENGINEERING
      Number format similar to scientific format but adjusted so that the exponent value is always a multiple of 3, allowing easier alignment with SI prefixes.

      For example: 

       0.0
 12.401
 100.0E3
 1.45E9
 12.3E-12

    • MIXED

      public static final DoubleFormat MIXED
      Number format that uses plain format for small numbers and scientific format for large numbers. The number thresholds can be configured through the plainFormatMinDecimalExponent and plainFormatMaxDecimalExponent properties.

      For example: 

       0.0
 12.401
 100000.0
 1.45E9
 1.23E-11

  • Method Details

    • values

      public static DoubleFormat[] values()
      Returns an array containing the constants of this enum type, in the order they are declared.
      Returns:
      an array containing the constants of this enum type, in the order they are declared

    • valueOf

      public static DoubleFormat valueOf(String name)
      Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
      Parameters:
      name - the name of the enum constant to be returned.
      Returns:
      the enum constant with the specified name
      Throws:
      IllegalArgumentException - if this enum type has no constant with the specified name
      NullPointerException - if the argument is null

    • builder

      public DoubleFormat.Builder builder()
      Creates a DoubleFormat.Builder for building formatter functions for this format type.
      Returns:
      builder instance