public abstract class NumberFormat extends Format
NumberFormat
has features designed to make it possible to format
numbers in any locale. It also supports different kinds of numbers, including integers (123), fixed-point numbers (123.4), percentages (12%), and
currency amounts ($123). All of these can be localized.
Usage:
NumberFormat f = NumberFormat.getInstance(); StringBuffer sb = f.format(new Double(123.45), new StringBuffer());
Or eventually it's possible to change number of decimals displayed
NumberFormat f = NumberFormat.getInstance(); f.setMaximumFractionDigits(2); StringBuffer sb = f.format(new Double(123.45559), new StringBuffer());
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:
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.myString = NumberFormat.getInstance().format(myNumber);
To format a number for a different Locale, specify it in the call toNumberFormat nf = NumberFormat.getInstance(); for (int i = 0; i < a.length; ++i) { output.println(nf.format(myNumber[i]) + "; "); }
getInstance
. You can also use aNumberFormat nf = NumberFormat.getInstance(Locale.FRENCH);
NumberFormat
to parse numbers: UsemyNumber = nf.parse(myString);
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
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 . |
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 and Description |
---|
NumberFormat() |
Modifier and Type | Method and Description |
---|---|
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 an object to produce a string.
|
static NumberFormat |
getCurrencyInstance()
Returns a currency format for the current default locale.
|
static NumberFormat |
getInstance()
Returns a general-purpose number format.
|
static NumberFormat |
getIntegerInstance()
Returns an integer number format for the current default 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 |
getPercentInstance()
Returns a percentage format for the current default locale.
|
int |
hashCode()
Overrides hashCode
|
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.
|
public static final int INTEGER_FIELD
FieldPosition
,
Constant Field Valuespublic static final int FRACTION_FIELD
FieldPosition
,
Constant Field Valuespublic NumberFormat()
public final StringBuffer format(Object number, StringBuffer toAppendTo, FieldPosition pos)
format
in class Format
number
- the object to formattoAppendTo
- where the text is to be appendedpos
- On input: an alignment field, if desired. On output: the offsets of the alignment field.IllegalArgumentException
- when the Format cannot format the given object.FieldPosition
public final String format(double number)
Format.format(java.lang.Object)
public final String format(long number)
Format.format(java.lang.Object)
public abstract StringBuffer format(double number, StringBuffer toAppendTo, FieldPosition pos)
Format.format(java.lang.Object)
public abstract StringBuffer format(long number, StringBuffer toAppendTo, FieldPosition pos)
Format.format(java.lang.Object)
public static final NumberFormat getInstance()
NumberFormat
instance for general-purpose number formattingpublic static final NumberFormat getNumberInstance()
public static final NumberFormat getIntegerInstance()
ROUND_HALF_EVEN
) for formatting, and to parse
only the integer part of an input string (see isParseIntegerOnly
). NOTE: java.math.BigDecimal is found in J2ME
CDC profiles such as J2ME Foundation Profile.public static final NumberFormat getCurrencyInstance()
public static final NumberFormat getPercentInstance()
public int getMaximumIntegerDigits()
setMaximumIntegerDigits(int)
public void setMaximumIntegerDigits(int newValue)
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()
setMinimumIntegerDigits(int)
public void setMinimumIntegerDigits(int newValue)
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()
setMaximumFractionDigits(int)
public void setMaximumFractionDigits(int newValue)
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()
setMinimumFractionDigits(int)
public void setMinimumFractionDigits(int newValue)
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()
Copyright © 2005–2017 Jean-Marie Dautelle, Werner Keil, V2COM. All rights reserved.