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:
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. 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. 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.
DecimalFormat, ChoiceFormat, Serialized Form| Modifier and Type | Class and Description |
|---|---|
static class |
NumberFormat.Field Defines constants that are used as attribute keys in the |
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.
FieldPosition, Constant Field Valuespublic 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.
FieldPosition, Constant Field Valuesprotected NumberFormat()
Sole constructor. (For invocation by subclass constructors, typically implicit.)
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.
format in class Format
number - the number to formattoAppendTo - the StringBuffer to which the formatted text is to be appendedpos - On input: an alignment field, if desired. On output: the offsets of the alignment field.toAppendTo
IllegalArgumentException - if number is null or not an instance of Number.NullPointerException - if toAppendTo or pos is nullArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARYFieldPositionpublic 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.
parseObject in class Format
source - A String, part of which should be parsed.pos - A ParsePosition object with index and error index information as described above.Number parsed from the string. In case of error, returns null.NullPointerException - if pos is null.public final String format(double number)
Specialization of format.
number - the double number to formatArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARYFormat.format(java.lang.Object)public final String format(long number)
Specialization of format.
number - the long number to formatArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARYFormat.format(java.lang.Object)public abstract StringBuffer format(double number,
StringBuffer toAppendTo,
FieldPosition pos) Specialization of format.
number - the double number to formattoAppendTo - the StringBuffer to which the formatted text is to be appendedpos - the field positionArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARYFormat.format(java.lang.Object)public abstract StringBuffer format(long number,
StringBuffer toAppendTo,
FieldPosition pos) Specialization of format.
number - the long number to formattoAppendTo - the StringBuffer to which the formatted text is to be appendedpos - the field positionArithmeticException - if rounding is needed with rounding mode being set to RoundingMode.UNNECESSARYFormat.format(java.lang.Object)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!
source - the String to parseparsePosition - the parse positionisParseIntegerOnly(), Format.parseObject(java.lang.String, java.text.ParsePosition)
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.
source - A String whose beginning should be parsed.Number parsed from the string.ParseException - if the beginning of the specified string cannot be parsed.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.
true if numbers should be parsed as integers only; false otherwisepublic void setParseIntegerOnly(boolean value)
Sets whether or not numbers should be parsed as integers only.
value - true if numbers should be parsed as integers only; false otherwiseisParseIntegerOnly()public static final NumberFormat getInstance()
Returns a general-purpose number format for the current default FORMAT locale. This is the same as calling getNumberInstance().
NumberFormat instance for general-purpose number formattingpublic static NumberFormat getInstance(Locale inLocale)
Returns a general-purpose number format for the specified locale. This is the same as calling getNumberInstance(inLocale).
inLocale - the desired localeNumberFormat instance for general-purpose number formattingpublic static final NumberFormat getNumberInstance()
Returns a general-purpose number format for the current default FORMAT locale.
This is equivalent to calling getNumberInstance(Locale.getDefault(Locale.Category.FORMAT)).
NumberFormat instance for general-purpose number formattingLocale.getDefault(java.util.Locale.Category), Locale.Category.FORMAT
public static NumberFormat getNumberInstance(Locale inLocale)
Returns a general-purpose number format for the specified locale.
inLocale - the desired localeNumberFormat instance for general-purpose number formattingpublic static final NumberFormat getIntegerInstance()
Returns an integer number format for the current default FORMAT 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).
This is equivalent to calling getIntegerInstance(Locale.getDefault(Locale.Category.FORMAT)).
getRoundingMode(), Locale.getDefault(java.util.Locale.Category), Locale.Category.FORMAT
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).
inLocale - the desired localegetRoundingMode()public static final NumberFormat getCurrencyInstance()
Returns a currency format for the current default FORMAT locale.
This is equivalent to calling getCurrencyInstance(Locale.getDefault(Locale.Category.FORMAT)).
NumberFormat instance for currency formattingLocale.getDefault(java.util.Locale.Category), Locale.Category.FORMAT
public static NumberFormat getCurrencyInstance(Locale inLocale)
Returns a currency format for the specified locale.
inLocale - the desired localeNumberFormat instance for currency formattingpublic static final NumberFormat getPercentInstance()
Returns a percentage format for the current default FORMAT locale.
This is equivalent to calling getPercentInstance(Locale.getDefault(Locale.Category.FORMAT)).
NumberFormat instance for percentage formattingLocale.getDefault(java.util.Locale.Category), Locale.Category.FORMAT
public static NumberFormat getPercentInstance(Locale inLocale)
Returns a percentage format for the specified locale.
inLocale - the desired localeNumberFormat instance for percentage formattingpublic 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.
NumberFormat instances are available.public int hashCode()
Overrides hashCode.
hashCode in class Object
Object.equals(java.lang.Object), System.identityHashCode(java.lang.Object)
public boolean equals(Object obj)
Overrides equals.
equals in class Object
obj - the reference object with which to compare.true if this object is the same as the obj argument; false otherwise.Object.hashCode(), HashMap
public Object clone()
Overrides Cloneable.
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.
true if grouping is used; false otherwisesetGroupingUsed(boolean)public void setGroupingUsed(boolean newValue)
Set whether or not grouping will be used in this format.
newValue - true if grouping is used; false otherwiseisGroupingUsed()public int getMaximumIntegerDigits()
Returns the maximum number of digits allowed in the integer portion of a number.
setMaximumIntegerDigits(int)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.
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.getMaximumIntegerDigits()public int getMinimumIntegerDigits()
Returns the minimum number of digits allowed in the integer portion of a number.
setMinimumIntegerDigits(int)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
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.getMinimumIntegerDigits()public int getMaximumFractionDigits()
Returns the maximum number of digits allowed in the fraction portion of a number.
setMaximumFractionDigits(int)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.
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.getMaximumFractionDigits()public int getMinimumFractionDigits()
Returns the minimum number of digits allowed in the fraction portion of a number.
setMinimumFractionDigits(int)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
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.getMinimumFractionDigits()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.
null
UnsupportedOperationException - if the number format class doesn't implement currency formattingpublic 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.
currency - the new currency to be used by this number formatUnsupportedOperationException - if the number format class doesn't implement currency formattingNullPointerException - if currency is nullpublic 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.
RoundingMode used for this NumberFormat.UnsupportedOperationException - The default implementation always throws this exceptionsetRoundingMode(RoundingMode)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.
roundingMode - The RoundingMode to be usedUnsupportedOperationException - The default implementation always throws this exceptionNullPointerException - if roundingMode is nullgetRoundingMode()
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