java.text
Class DigitList

java.lang.Object
  java.text.DigitList

All Implemented Interfaces:

Cloneable

final class DigitList

extends Object

implements Cloneable

Digit List. Private to DecimalFormat. Handles the transcoding between numeric values and strings of characters. Only handles non-negative numbers. The division of labor between DigitList and DecimalFormat is that DigitList handles the radix 10 representation issues; DecimalFormat handles the locale-specific issues such as positive/negative, grouping, decimal point, currency, and so on. A DigitList is really a representation of a floating point value. It may be an integer value; we assume that a double has sufficient precision to represent all digits of a long. The DigitList representation consists of a string of characters, which are the digits radix 10, from '0' to '9'. It also has a radix 10 exponent associated with it. The value represented by a DigitList object can be computed by mulitplying the fraction f, where 0 <= f < 1, derived by placing all the digits of the list to the right of the decimal point, by 10^exponent.

Author:

Mark Davis, Alan Liu

See Also:

Locale, Format, NumberFormat, DecimalFormat, ChoiceFormat, MessageFormat

Field Summary

int	count
static int	DBL_DIG
int	decimalAt These data members are intentionally public and can be set directly.
char[]	digits
private static char[]	LONG_MIN_REP
static int	MAX_COUNT The maximum number of significant digits in an IEEE 754 double, that is, in a Java double.
private StringBuffer	tempBuffer

Constructor Summary

(package private)

DigitList()

Method Summary

void	append(char digit) Appends a digit to the list.
void	clear() Clears out the digits.
Object	clone() Creates a copy of this object.
boolean	equals(Object obj) equality test between two digit lists.
(package private) boolean	fitsIntoLong(boolean isPositive, boolean ignoreNegativeZero) Return true if the number represented by this object can fit into a long.
double	getDouble() Utility routine to get the value of the digit list If (count == 0) this throws a NumberFormatException, which mimics Long.parseLong().
long	getLong() Utility routine to get the value of the digit list.
private StringBuffer	getStringBuffer()
int	hashCode() Generates the hash code for the digit list.
private boolean	isLongMIN_VALUE() Returns true if this DigitList represents Long.MIN_VALUE; false, otherwise.
(package private) boolean	isZero() Return true if the represented number is zero.
private static int	parseInt(char[] str, int offset)
private void	round(int maximumDigits) Round the representation to the given number of digits.
void	set(double source, int maximumFractionDigits) Set the digit list to a representation of the given double value.
(package private) void	set(double source, int maximumDigits, boolean fixedPoint) Set the digit list to a representation of the given double value.
void	set(long source) Utility routine to set the value of the digit list from a long
void	set(long source, int maximumDigits) Set the digit list to a representation of the given long value.
private boolean	shouldRoundUp(int maximumDigits) Return true if truncating the representation to the given number of digits will result in an increment to the last digit.
String	toString() Returns a string representation of the object.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

MAX_COUNT

public static final int MAX_COUNT

The maximum number of significant digits in an IEEE 754 double, that is, in a Java double. This must not be increased, or garbage digits will be generated, and should not be decreased, or accuracy will be lost.

See Also:

Constant Field Values

DBL_DIG

public static final int DBL_DIG

See Also:

Constant Field Values

decimalAt

public int decimalAt

These data members are intentionally public and can be set directly. The value represented is given by placing the decimal point before digits[decimalAt]. If decimalAt is < 0, then leading zeros between the decimal point and the first nonzero digit are implied. If decimalAt is > count, then trailing zeros between the digits[count-1] and the decimal point are implied. Equivalently, the represented value is given by f * 10^decimalAt. Here f is a value 0.1 <= f < 1 arrived at by placing the digits in Digits to the right of the decimal. DigitList is normalized, so if it is non-zero, figits[0] is non-zero. We don't allow denormalized numbers because our exponent is effectively of unlimited magnitude. The count value contains the number of significant digits present in digits[]. Zero is represented by any DigitList with count == 0 or with each digits[i] for all i <= count == '0'.

count

public int count

digits

public char[] digits

LONG_MIN_REP

private static final char[] LONG_MIN_REP

tempBuffer

private StringBuffer tempBuffer

Constructor Detail

DigitList

DigitList()

Method Detail

isZero

boolean isZero()

Return true if the represented number is zero.

clear

public void clear()

Clears out the digits. Use before appending them. Typically, you set a series of digits with append, then at the point you hit the decimal point, you set myDigitList.decimalAt = myDigitList.count; then go on appending digits.

append

public void append(char digit)

Appends a digit to the list. Ignores all digits over MAX_COUNT, since they are not significant for either longs or doubles.

getDouble

public final double getDouble()

Utility routine to get the value of the digit list If (count == 0) this throws a NumberFormatException, which mimics Long.parseLong().

getLong

public final long getLong()

Utility routine to get the value of the digit list. If (count == 0) this returns 0, unlike Long.parseLong().

fitsIntoLong

boolean fitsIntoLong(boolean isPositive,
                     boolean ignoreNegativeZero)

Return true if the number represented by this object can fit into a long.

Parameters:

isPositive - true if this number should be regarded as positive

ignoreNegativeZero - true if -0 should be regarded as identical to +0; otherwise they are considered distinct

Returns:

true if this number fits into a Java long

set

public final void set(double source,
                      int maximumFractionDigits)

Set the digit list to a representation of the given double value. This method supports fixed-point notation.

Parameters:

source - Value to be converted; must not be Inf, -Inf, Nan, or a value <= 0.

maximumFractionDigits - The most fractional digits which should be converted.

set

final void set(double source,
               int maximumDigits,
               boolean fixedPoint)

Set the digit list to a representation of the given double value. This method supports both fixed-point and exponential notation.

Parameters:

source - Value to be converted; must not be Inf, -Inf, Nan, or a value <= 0.

maximumDigits - The most fractional or total digits which should be converted.

fixedPoint - If true, then maximumDigits is the maximum fractional digits to be converted. If false, total digits.

round

private final void round(int maximumDigits)

Round the representation to the given number of digits.

Parameters:

maximumDigits - The maximum number of digits to be shown. Upon return, count will be less than or equal to maximumDigits.

shouldRoundUp

private boolean shouldRoundUp(int maximumDigits)

Return true if truncating the representation to the given number of digits will result in an increment to the last digit. This method implements half-even rounding, the default rounding mode. [bnf]

Parameters:

maximumDigits - the number of digits to keep, from 0 to count-1. If 0, then all digits are rounded away, and this method returns true if a one should be generated (e.g., formatting 0.09 with "#.#").

Returns:

true if digit maximumDigits-1 should be incremented

set

public final void set(long source)

Utility routine to set the value of the digit list from a long

set

public final void set(long source,
                      int maximumDigits)

Set the digit list to a representation of the given long value.

Parameters:

source - Value to be converted; must be >= 0 or == Long.MIN_VALUE.

maximumDigits - The most digits which should be converted. If maximumDigits is lower than the number of significant digits in source, the representation will be rounded. Ignored if <= 0.

equals

public boolean equals(Object obj)

equality test between two digit lists.

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(), Hashtable

hashCode

public int hashCode()

Generates the hash code for the digit list.

Overrides:

hashCode in class Object

Returns:

a hash code value for this object.

See Also:

Object.equals(java.lang.Object), Hashtable

clone

public Object clone()

Creates a copy of this object.

Overrides:

clone in class Object

Returns:

a clone of this instance.

See Also:

Cloneable

isLongMIN_VALUE

private boolean isLongMIN_VALUE()

Returns true if this DigitList represents Long.MIN_VALUE; false, otherwise. This is required so that getLong() works.

parseInt

private static final int parseInt(char[] str,
                                  int offset)

toString

public String toString()

Description copied from class: Object

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Overrides:

toString in class Object

Returns:

a string representation of the object.

getStringBuffer

private StringBuffer getStringBuffer()