java.text

## Class NumberFormat

- java.lang.Object
- - java.text.Format
  - - java.text.NumberFormat

- All Implemented Interfaces:
    Serializable, Cloneable
  Direct Known Subclasses:
    ChoiceFormat, DecimalFormat

      public abstract class NumberFormat
      extends Format

  `NumberFormat` is the abstract base class for all number formats. This class provides the interface for formatting and parsing numbers. `NumberFormat` also provides methods for determining which locales have number formats, and what their names are.

  `NumberFormat` helps you to format and parse numbers for any locale. Your code can be completely independent of the locale conventions for decimal points, thousands-separators, or even the particular decimal digits used, or whether the number format is even decimal.

  To format a number for the current Locale, use one of the factory class methods:

  >       myString = NumberFormat.getInstance().format(myNumber);

  If you are formatting multiple numbers, it is more efficient to get the format and use it multiple times so that the system doesn't have to fetch the information about the local language and country conventions multiple times.

  >      NumberFormat nf = NumberFormat.getInstance();
  >      for (int i = 0; i < myNumber.length; ++i) {
  >          output.println(nf.format(myNumber[i]) + "; ");
  >      }

  To format a number for a different Locale, specify it in the call to `getInstance`.

  >      NumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);

  You can also use a `NumberFormat` to parse numbers:

  >      myNumber = nf.parse(myString);

  Use `getInstance` or `getNumberInstance` to get the normal number format. Use `getIntegerInstance` to get an integer number format. Use `getCurrencyInstance` to get the currency number format. And use `getPercentInstance` to get a format for displaying percentages. With this format, a fraction like 0.53 is displayed as 53%.

  You can also control the display of numbers with such methods as `setMinimumFractionDigits`. If you want even more control over the format or parsing, or want to give your users more control, you can try casting the `NumberFormat` you get from the factory methods to a `DecimalFormat`. This will work for the vast majority of locales; just remember to put it in a `try` block in case you encounter an unusual one.

  NumberFormat and DecimalFormat are designed such that some controls work for formatting and others work for parsing. The following is the detailed description for each these control methods,

  setParseIntegerOnly : only affects parsing, e.g. if true, "3456.78" -> 3456 (and leaves the parse position just after index 6) if false, "3456.78" -> 3456.78 (and leaves the parse position just after index 8) This is independent of formatting. If you want to not show a decimal point where there might be no digits after the decimal point, use setDecimalSeparatorAlwaysShown.

  setDecimalSeparatorAlwaysShown : only affects formatting, and only where there might be no digits after the decimal point, such as with a pattern like "#,##0.##", e.g., if true, 3456.00 -> "3,456." if false, 3456.00 -> "3456" This is independent of parsing. If you want parsing to stop at the decimal point, use setParseIntegerOnly.

  You can also use forms of the `parse` and `format` methods with `ParsePosition` and `FieldPosition` to allow you to:

  - progressively parse through pieces of a string
  - align the decimal point and other areas
  For example, you can align numbers in two ways:
  1. If you are using a monospaced font with spacing for alignment, you can pass the `FieldPosition` in your format call, with `field` = `INTEGER_FIELD`. On output, `getEndIndex` will be set to the offset between the last character of the integer and the decimal. Add (desiredSpaceCount - getEndIndex) spaces at the front of the string.
  2. If you are using proportional fonts, instead of padding with spaces, measure the width of the string in pixels from the start to `getEndIndex`. Then move the pen by (desiredPixelWidth - widthToAlignmentPoint) before drawing the text. It also works where there is no decimal, but possibly additional characters at the end, e.g., with parentheses in negative numbers: "(12)" for -12.

  #### Synchronization

  Number formats are generally not synchronized. It is recommended to create separate format instances for each thread. If multiple threads access a format concurrently, it must be synchronized externally.

  Author:
    Mark Davis, Helena Shih
  See Also:
    `DecimalFormat`, `ChoiceFormat`, Serialized Form

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Class and Description
    --- | ---
    `static class` | `NumberFormat.Field` Defines constants that are used as attribute keys in the `AttributedCharacterIterator` returned from `NumberFormat.formatToCharacterIterator` and as field identifiers in `FieldPosition`.

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static int` | `FRACTION_FIELD` Field constant used to construct a FieldPosition object.
    `static int` | `INTEGER_FIELD` Field constant used to construct a FieldPosition object.

  - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `NumberFormat()` Sole constructor.

  - ### Method Summary

    All Methods Static Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `Object` | `clone()` Overrides Cloneable
    `boolean` | `equals(Object obj)` Overrides equals
    `String` | `format(double number)` Specialization of format.
    `abstract StringBuffer` | `format(double number, StringBuffer toAppendTo, FieldPosition pos)` Specialization of format.
    `String` | `format(long number)` Specialization of format.
    `abstract StringBuffer` | `format(long number, StringBuffer toAppendTo, FieldPosition pos)` Specialization of format.
    `StringBuffer` | `format(Object number, StringBuffer toAppendTo, FieldPosition pos)` Formats a number and appends the resulting text to the given string buffer.
    `static Locale[]` | `getAvailableLocales()` Returns an array of all locales for which the `get*Instance` methods of this class can return localized instances.
    `Currency` | `getCurrency()` Gets the currency used by this number format when formatting currency values.
    `static NumberFormat` | `getCurrencyInstance()` Returns a currency format for the current default locale.
    `static NumberFormat` | `getCurrencyInstance(Locale inLocale)` Returns a currency format for the specified locale.
    `static NumberFormat` | `getInstance()` Returns a general-purpose number format for the current default locale.
    `static NumberFormat` | `getInstance(Locale inLocale)` Returns a general-purpose number format for the specified locale.
    `static NumberFormat` | `getIntegerInstance()` Returns an integer number format for the current default locale.
    `static NumberFormat` | `getIntegerInstance(Locale inLocale)` Returns an integer number format for the specified locale.
    `int` | `getMaximumFractionDigits()` Returns the maximum number of digits allowed in the fraction portion of a number.
    `int` | `getMaximumIntegerDigits()` Returns the maximum number of digits allowed in the integer portion of a number.
    `int` | `getMinimumFractionDigits()` Returns the minimum number of digits allowed in the fraction portion of a number.
    `int` | `getMinimumIntegerDigits()` Returns the minimum number of digits allowed in the integer portion of a number.
    `static NumberFormat` | `getNumberInstance()` Returns a general-purpose number format for the current default locale.
    `static NumberFormat` | `getNumberInstance(Locale inLocale)` Returns a general-purpose number format for the specified locale.
    `static NumberFormat` | `getPercentInstance()` Returns a percentage format for the current default locale.
    `static NumberFormat` | `getPercentInstance(Locale inLocale)` Returns a percentage format for the specified locale.
    `RoundingMode` | `getRoundingMode()` Gets the `RoundingMode` used in this NumberFormat.
    `int` | `hashCode()` Overrides hashCode
    `boolean` | `isGroupingUsed()` Returns true if grouping is used in this format.
    `boolean` | `isParseIntegerOnly()` Returns true if this format will parse numbers as integers only.
    `Number` | `parse(String source)` Parses text from the beginning of the given string to produce a number.
    `abstract Number` | `parse(String source, ParsePosition parsePosition)` Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double.
    `Object` | `parseObject(String source, ParsePosition pos)` Parses text from a string to produce a `Number`.
    `void` | `setCurrency(Currency currency)` Sets the currency used by this number format when formatting currency values.
    `void` | `setGroupingUsed(boolean newValue)` Set whether or not grouping will be used in this format.
    `void` | `setMaximumFractionDigits(int newValue)` Sets the maximum number of digits allowed in the fraction portion of a number.
    `void` | `setMaximumIntegerDigits(int newValue)` Sets the maximum number of digits allowed in the integer portion of a number.
    `void` | `setMinimumFractionDigits(int newValue)` Sets the minimum number of digits allowed in the fraction portion of a number.
    `void` | `setMinimumIntegerDigits(int newValue)` Sets the minimum number of digits allowed in the integer portion of a number.
    `void` | `setParseIntegerOnly(boolean value)` Sets whether or not numbers should be parsed as integers only.
    `void` | `setRoundingMode(RoundingMode roundingMode)` Sets the `RoundingMode` used in this NumberFormat.

    - ### Methods inherited from class java.text.Format

      `format, formatToCharacterIterator, parseObject`

    - ### Methods inherited from class java.lang.Object

      `finalize, getClass, notify, notifyAll, toString, wait, wait, wait`

- - ### Field Detail

    - #### INTEGER_FIELD

          public static final int INTEGER_FIELD

      Field constant used to construct a FieldPosition object. Signifies that the position of the integer part of a formatted number should be returned.
      See Also:
        `FieldPosition`, Constant Field Values

    - #### FRACTION_FIELD

          public static final int FRACTION_FIELD

      Field constant used to construct a FieldPosition object. Signifies that the position of the fraction part of a formatted number should be returned.
      See Also:
        `FieldPosition`, Constant Field Values

  - ### Constructor Detail

    - #### NumberFormat

          protected NumberFormat()

      Sole constructor. (For invocation by subclass constructors, typically implicit.)

  - ### Method Detail

    - #### format

          public StringBuffer format(Object number,
                                     StringBuffer toAppendTo,
                                     FieldPosition pos)

      Formats a number and appends the resulting text to the given string buffer. The number can be of any subclass of `Number`.

      This implementation extracts the number's value using `Number.longValue()` for all integral type values that can be converted to `long` without loss of information, including `BigInteger` values with a `bit length` of less than 64, and `Number.doubleValue()` for all other types. It then calls `format(long,java.lang.StringBuffer,java.text.FieldPosition)` or `format(double,java.lang.StringBuffer,java.text.FieldPosition)`. This may result in loss of magnitude information and precision for `BigInteger` and `BigDecimal` values.

      Specified by:
        `format` in class `Format`
      Parameters:
        `number` - the number to format
        `toAppendTo` - the `StringBuffer` to which the formatted text is to be appended
        `pos` - On input: an alignment field, if desired. On output: the offsets of the alignment field.
      Returns:
        the value passed in as `toAppendTo`
      Throws:
        `IllegalArgumentException` - if `number` is null or not an instance of `Number`.
        `NullPointerException` - if `toAppendTo` or `pos` is null
        `ArithmeticException` - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
      See Also:
        `FieldPosition`

    - #### parseObject

          public final Object parseObject(String source,
                                          ParsePosition pos)

      Parses text from a string to produce a `Number`.

      The method attempts to parse text starting at the index given by `pos`. If parsing succeeds, then the index of `pos` is updated to the index after the last character used (parsing does not necessarily use all characters up to the end of the string), and the parsed number is returned. The updated `pos` can be used to indicate the starting point for the next call to this method. If an error occurs, then the index of `pos` is not changed, the error index of `pos` is set to the index of the character where the error occurred, and null is returned.

      See the `parse(String, ParsePosition)` method for more information on number parsing.

      Specified by:
        `parseObject` in class `Format`
      Parameters:
        `source` - A `String`, part of which should be parsed.
        `pos` - A `ParsePosition` object with index and error index information as described above.
      Returns:
        A `Number` parsed from the string. In case of error, returns null.
      Throws:
        `NullPointerException` - if `pos` is null.

    - #### format

          public final String format(double number)

      Specialization of format.
      Throws:
        `ArithmeticException` - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
      See Also:
        `Format.format(java.lang.Object)`

    - #### format

          public final String format(long number)

      Specialization of format.
      Throws:
        `ArithmeticException` - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
      See Also:
        `Format.format(java.lang.Object)`

    - #### format

          public abstract StringBuffer format(double number,
                                              StringBuffer toAppendTo,
                                              FieldPosition pos)

      Specialization of format.
      Throws:
        `ArithmeticException` - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
      See Also:
        `Format.format(java.lang.Object)`

    - #### format

          public abstract StringBuffer format(long number,
                                              StringBuffer toAppendTo,
                                              FieldPosition pos)

      Specialization of format.
      Throws:
        `ArithmeticException` - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARY
      See Also:
        `Format.format(java.lang.Object)`

    - #### parse

          public abstract Number parse(String source,
                                       ParsePosition parsePosition)

      Returns a Long if possible (e.g., within the range [Long.MIN_VALUE, Long.MAX_VALUE] and with no decimals), otherwise a Double. If IntegerOnly is set, will stop at a decimal point (or equivalent; e.g., for rational numbers "1 2/3", will stop after the 1). Does not throw an exception; if no object can be parsed, index is unchanged!
      See Also:
        `isParseIntegerOnly()`, `Format.parseObject(java.lang.String, java.text.ParsePosition)`

    - #### parse

          public Number parse(String source)
                       throws ParseException

      Parses text from the beginning of the given string to produce a number. The method may not use the entire text of the given string.

      See the `parse(String, ParsePosition)` method for more information on number parsing.

      Parameters:
        `source` - A `String` whose beginning should be parsed.
      Returns:
        A `Number` parsed from the string.
      Throws:
        `ParseException` - if the beginning of the specified string cannot be parsed.

    - #### isParseIntegerOnly

          public boolean isParseIntegerOnly()

      Returns true if this format will parse numbers as integers only. For example in the English locale, with ParseIntegerOnly true, the string "1234." would be parsed as the integer value 1234 and parsing would stop at the "." character. Of course, the exact format accepted by the parse operation is locale dependant and determined by sub-classes of NumberFormat.

    - #### setParseIntegerOnly

          public void setParseIntegerOnly(boolean value)

      Sets whether or not numbers should be parsed as integers only.
      See Also:
        `isParseIntegerOnly()`

    - #### getInstance

          public static final NumberFormat getInstance()

      Returns a general-purpose number format for the current default locale. This is the same as calling `getNumberInstance()`.

    - #### getInstance

          public static NumberFormat getInstance(Locale inLocale)

      Returns a general-purpose number format for the specified locale. This is the same as calling `getNumberInstance(inLocale)`.

    - #### getNumberInstance

          public static final NumberFormat getNumberInstance()

      Returns a general-purpose number format for the current default locale.

    - #### getNumberInstance

          public static NumberFormat getNumberInstance(Locale inLocale)

      Returns a general-purpose number format for the specified locale.

    - #### getIntegerInstance

          public static final NumberFormat getIntegerInstance()

      Returns an integer number format for the current default locale. The returned number format is configured to round floating point numbers to the nearest integer using half-even rounding (see `RoundingMode.HALF_EVEN`) for formatting, and to parse only the integer part of an input string (see `isParseIntegerOnly`).
      Returns:
        a number format for integer values
      Since:
        1.4
      See Also:
        `getRoundingMode()`

    - #### getIntegerInstance

          public static NumberFormat getIntegerInstance(Locale inLocale)

      Returns an integer number format for the specified locale. The returned number format is configured to round floating point numbers to the nearest integer using half-even rounding (see `RoundingMode.HALF_EVEN`) for formatting, and to parse only the integer part of an input string (see `isParseIntegerOnly`).
      Returns:
        a number format for integer values
      Since:
        1.4
      See Also:
        `getRoundingMode()`

    - #### getCurrencyInstance

          public static final NumberFormat getCurrencyInstance()

      Returns a currency format for the current default locale.

    - #### getCurrencyInstance

          public static NumberFormat getCurrencyInstance(Locale inLocale)

      Returns a currency format for the specified locale.

    - #### getPercentInstance

          public static final NumberFormat getPercentInstance()

      Returns a percentage format for the current default locale.

    - #### getPercentInstance

          public static NumberFormat getPercentInstance(Locale inLocale)

      Returns a percentage format for the specified locale.

    - #### getAvailableLocales

          public static Locale[] getAvailableLocales()

      Returns an array of all locales for which the `get*Instance` methods of this class can return localized instances. The returned array represents the union of locales supported by the Java runtime and by installed `NumberFormatProvider` implementations. It must contain at least a `Locale` instance equal to `Locale.US`.
      Returns:
        An array of locales for which localized `NumberFormat` instances are available.

    - #### hashCode

          public int hashCode()

      Overrides hashCode
      Overrides:
        `hashCode` in class `Object`
      Returns:
        a hash code value for this object.
      See Also:
        `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

    - #### equals

          public boolean equals(Object obj)

      Overrides equals
      Overrides:
        `equals` in class `Object`
      Parameters:
        `obj` - the reference object with which to compare.
      Returns:
        `true` if this object is the same as the obj argument; `false` otherwise.
      See Also:
        `Object.hashCode()`, `HashMap`

    - #### clone

          public Object clone()

      Overrides Cloneable
      Overrides:
        `clone` in class `Format`
      Returns:
        a clone of this instance.
      See Also:
        `Cloneable`

    - #### isGroupingUsed

          public boolean isGroupingUsed()

      Returns true if grouping is used in this format. For example, in the English locale, with grouping on, the number 1234567 might be formatted as "1,234,567". The grouping separator as well as the size of each group is locale dependant and is determined by sub-classes of NumberFormat.
      See Also:
        `setGroupingUsed(boolean)`

    - #### setGroupingUsed

          public void setGroupingUsed(boolean newValue)

      Set whether or not grouping will be used in this format.
      See Also:
        `isGroupingUsed()`

    - #### getMaximumIntegerDigits

          public int getMaximumIntegerDigits()

      Returns the maximum number of digits allowed in the integer portion of a number.
      See Also:
        `setMaximumIntegerDigits(int)`

    - #### setMaximumIntegerDigits

          public void setMaximumIntegerDigits(int newValue)

      Sets the maximum number of digits allowed in the integer portion of a number. maximumIntegerDigits must be >= minimumIntegerDigits. If the new value for maximumIntegerDigits is less than the current value of minimumIntegerDigits, then minimumIntegerDigits will also be set to the new value.
      Parameters:
        `newValue` - the maximum number of integer digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
      See Also:
        `getMaximumIntegerDigits()`

    - #### getMinimumIntegerDigits

          public int getMinimumIntegerDigits()

      Returns the minimum number of digits allowed in the integer portion of a number.
      See Also:
        `setMinimumIntegerDigits(int)`

    - #### setMinimumIntegerDigits

          public void setMinimumIntegerDigits(int newValue)

      Sets the minimum number of digits allowed in the integer portion of a number. minimumIntegerDigits must be <= maximumIntegerDigits. If the new value for minimumIntegerDigits exceeds the current value of maximumIntegerDigits, then maximumIntegerDigits will also be set to the new value
      Parameters:
        `newValue` - the minimum number of integer digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
      See Also:
        `getMinimumIntegerDigits()`

    - #### getMaximumFractionDigits

          public int getMaximumFractionDigits()

      Returns the maximum number of digits allowed in the fraction portion of a number.
      See Also:
        `setMaximumFractionDigits(int)`

    - #### setMaximumFractionDigits

          public void setMaximumFractionDigits(int newValue)

      Sets the maximum number of digits allowed in the fraction portion of a number. maximumFractionDigits must be >= minimumFractionDigits. If the new value for maximumFractionDigits is less than the current value of minimumFractionDigits, then minimumFractionDigits will also be set to the new value.
      Parameters:
        `newValue` - the maximum number of fraction digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
      See Also:
        `getMaximumFractionDigits()`

    - #### getMinimumFractionDigits

          public int getMinimumFractionDigits()

      Returns the minimum number of digits allowed in the fraction portion of a number.
      See Also:
        `setMinimumFractionDigits(int)`

    - #### setMinimumFractionDigits

          public void setMinimumFractionDigits(int newValue)

      Sets the minimum number of digits allowed in the fraction portion of a number. minimumFractionDigits must be <= maximumFractionDigits. If the new value for minimumFractionDigits exceeds the current value of maximumFractionDigits, then maximumIntegerDigits will also be set to the new value
      Parameters:
        `newValue` - the minimum number of fraction digits to be shown; if less than zero, then zero is used. The concrete subclass may enforce an upper limit to this value appropriate to the numeric type being formatted.
      See Also:
        `getMinimumFractionDigits()`

    - #### getCurrency

          public Currency getCurrency()

      Gets the currency used by this number format when formatting currency values. The initial value is derived in a locale dependent way. The returned value may be null if no valid currency could be determined and no currency has been set using `setCurrency`.

      The default implementation throws `UnsupportedOperationException`.

      Returns:
        the currency used by this number format, or `null`
      Throws:
        `UnsupportedOperationException` - if the number format class doesn't implement currency formatting
      Since:
        1.4

    - #### setCurrency

          public void setCurrency(Currency currency)

      Sets the currency used by this number format when formatting currency values. This does not update the minimum or maximum number of fraction digits used by the number format.

      The default implementation throws `UnsupportedOperationException`.

      Parameters:
        `currency` - the new currency to be used by this number format
      Throws:
        `UnsupportedOperationException` - if the number format class doesn't implement currency formatting
        `NullPointerException` - if `currency` is null
      Since:
        1.4

    - #### getRoundingMode

          public RoundingMode getRoundingMode()

      Gets the `RoundingMode` used in this NumberFormat. The default implementation of this method in NumberFormat always throws `UnsupportedOperationException`. Subclasses which handle different rounding modes should override this method.
      Returns:
        The `RoundingMode` used for this NumberFormat.
      Throws:
        `UnsupportedOperationException` - The default implementation always throws this exception
      Since:
        1.6
      See Also:
        `setRoundingMode(RoundingMode)`

    - #### setRoundingMode

          public void setRoundingMode(RoundingMode roundingMode)

      Sets the `RoundingMode` used in this NumberFormat. The default implementation of this method in NumberFormat always throws `UnsupportedOperationException`. Subclasses which handle different rounding modes should override this method.
      Parameters:
        `roundingMode` - The `RoundingMode` to be used
      Throws:
        `UnsupportedOperationException` - The default implementation always throws this exception
        `NullPointerException` - if `roundingMode` is null
      Since:
        1.6
      See Also:
        `getRoundingMode()`

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