java.text
class NumberFormat

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

All Implemented Interfaces:

Serializable, Cloneable

Direct Known Subclasses:

ChoiceFormat, DecimalFormat

Most common way to construct:

NumberFormat nf = NumberFormat.getInstance();

Based on 147 examples

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);
 

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

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

 myNumber = nf.parse(myString);
 

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

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.

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.

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.

NumberFormat

protected NumberFormat()

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

clone

public Object clone()

Overrides Cloneable

Overrides:

clone in class Format

equals

public boolean equals(Object obj)

Overrides equals

Overrides:

equals in class Object

Parameters:

obj

format

public final String format(double number)

Specialization of format.

Parameters:

number

format

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

Specialization of format.

Parameters:

number

toAppendTo

pos

format

public final String format(long number)

Specialization of format.

Parameters:

number

format

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

Specialization of format.

Parameters:

number

toAppendTo

pos

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 {@link java.lang.Number}.

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

Overrides:

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

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 {@link java.text.spi.NumberFormatProvider NumberFormatProvider} implementations. It must contain at least a Locale instance equal to {@link java.util.Locale#US Locale.US}.

Returns:

An array of locales for which localized NumberFormat instances are available.

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 {@link #setCurrency(java.util.Currency) setCurrency}.

The default implementation throws UnsupportedOperationException.

Returns:

the currency used by this number format, or null

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.

Parameters:

inLocale

getInstance

public static final NumberFormat getInstance()

Returns a general-purpose number format for the current default locale. This is the same as calling {@link #getNumberInstance() getNumberInstance()}.

getInstance

public static NumberFormat getInstance(Locale inLocale)

Returns a general-purpose number format for the specified locale. This is the same as calling {@link #getNumberInstance(java.util.Locale) getNumberInstance(inLocale)}.

Parameters:

inLocale

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 {@link java.math.RoundingMode#HALF_EVEN RoundingMode.HALF_EVEN}) for formatting, and to parse only the integer part of an input string (see {@link #isParseIntegerOnly isParseIntegerOnly}).

Returns:

a number format for integer values

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 {@link java.math.RoundingMode#HALF_EVEN RoundingMode.HALF_EVEN}) for formatting, and to parse only the integer part of an input string (see {@link #isParseIntegerOnly isParseIntegerOnly}).

Parameters:

inLocale

Returns:

a number format for integer values

getMaximumFractionDigits

public int getMaximumFractionDigits()

Returns the maximum number of digits allowed in the fraction portion of a number.

getMaximumIntegerDigits

public int getMaximumIntegerDigits()

Returns the maximum number of digits allowed in the integer portion of a number.

getMinimumFractionDigits

public int getMinimumFractionDigits()

Returns the minimum number of digits allowed in the fraction portion of a number.

getMinimumIntegerDigits

public int getMinimumIntegerDigits()

Returns the minimum number of digits allowed in the integer portion of a number.

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.

Parameters:

inLocale

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.

Parameters:

inLocale

getRoundingMode

public RoundingMode getRoundingMode()

Gets the {@link java.math.RoundingMode} used in this NumberFormat. The default implementation of this method in NumberFormat always throws {@link java.lang.UnsupportedOperationException}. Subclasses which handle different rounding modes should override this method.

Returns:

The RoundingMode used for this NumberFormat.

hashCode

public int hashCode()

Overrides hashCode

Overrides:

hashCode in class Object

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.

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.

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 {@link #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.

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!

Parameters:

source

parsePosition

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 {@link #parse(String, ParsePosition)} method for more information on number parsing.

Overrides:

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.

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

setGroupingUsed

public void setGroupingUsed(boolean newValue)

Set whether or not grouping will be used in this format.

Parameters:

newValue

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.

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.

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.

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.

setParseIntegerOnly

public void setParseIntegerOnly(boolean value)

Sets whether or not numbers should be parsed as integers only.

Parameters:

value

setRoundingMode

public void setRoundingMode(RoundingMode roundingMode)

Sets the {@link java.math.RoundingMode} used in this NumberFormat. The default implementation of this method in NumberFormat always throws {@link java.lang.UnsupportedOperationException}. Subclasses which handle different rounding modes should override this method.

Parameters:

roundingMode - The RoundingMode to be used