format(obj,
new StringBuffer(), new FieldPosition(0)).toString();

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 NumberFormat.format(long,java.lang.StringBuffer,java.text.FieldPosition) or NumberFormat.format(double,java.lang.StringBuffer,java.text.FieldPosition). This may result in loss of magnitude information and precision for BigInteger and BigDecimal values.
Returns: the value passed in as toAppendTo
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.
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,

Each attribute key of the AttributedCharacterIterator will be of type Field. It is up to each Format implementation to define what the legal values are for each attribute in the AttributedCharacterIterator, but typically the attribute key is also used as the attribute value.

The default implementation creates an AttributedCharacterIterator with no attributes. Subclasses that support fields should override this and create an AttributedCharacterIterator with meaningful attributes.
Returns: AttributedCharacterIterator describing the formatted value.
Parameters:
- obj - The object to format
Throws:
- NullPointerException - if obj is null.
- IllegalArgumentException - when the Format cannot format the given object.
Since: 1.4

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

See the NumberFormat.parse(String, ParsePosition) method for more information on number parsing.
Returns: A Number parsed from the string.
Parameters:
- source - A String whose beginning should be parsed.
Throws:
- ParseException - if the beginning of the specified string cannot be parsed.

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 NumberFormat.parse(String, ParsePosition) method for more information on number parsing.
Returns: A Number parsed from the string. In case of error, returns null.
Parameters:
- source - A String, part of which should be parsed.
- pos - A ParsePosition object with index and error index information as described above.
Throws:
- NullPointerException - if pos is null.

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