Java example source code file (DigitList.java)
The DigitList.java Java example source code/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
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*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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/*
* (C) Copyright Taligent, Inc. 1996, 1997 - All Rights Reserved
* (C) Copyright IBM Corp. 1996 - 1998 - All Rights Reserved
*
* The original version of this source code and documentation is copyrighted
* and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
* materials are provided under terms of a License Agreement between Taligent
* and Sun. This technology is protected by multiple US and International
* patents. This notice and attribution to Taligent may not be removed.
* Taligent is a registered trademark of Taligent, Inc.
*
*/
package java.text;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;
import sun.misc.FloatingDecimal;
/**
* 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.
*
* @see Locale
* @see Format
* @see NumberFormat
* @see DecimalFormat
* @see ChoiceFormat
* @see MessageFormat
* @author Mark Davis, Alan Liu
*/
final class DigitList implements Cloneable {
/**
* 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.
*/
public static final int MAX_COUNT = 19; // == Long.toString(Long.MAX_VALUE).length()
/**
* 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'.
*/
public int decimalAt = 0;
public int count = 0;
public char[] digits = new char[MAX_COUNT];
private char[] data;
private RoundingMode roundingMode = RoundingMode.HALF_EVEN;
private boolean isNegative = false;
/**
* Return true if the represented number is zero.
*/
boolean isZero() {
for (int i=0; i < count; ++i) {
if (digits[i] != '0') {
return false;
}
}
return true;
}
/**
* Set the rounding mode
*/
void setRoundingMode(RoundingMode r) {
roundingMode = r;
}
/**
* 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.
*/
public void clear () {
decimalAt = 0;
count = 0;
}
/**
* Appends a digit to the list, extending the list when necessary.
*/
public void append(char digit) {
if (count == digits.length) {
char[] data = new char[count + 100];
System.arraycopy(digits, 0, data, 0, count);
digits = data;
}
digits[count++] = digit;
}
/**
* Utility routine to get the value of the digit list
* If (count == 0) this throws a NumberFormatException, which
* mimics Long.parseLong().
*/
public final double getDouble() {
if (count == 0) {
return 0.0;
}
StringBuffer temp = getStringBuffer();
temp.append('.');
temp.append(digits, 0, count);
temp.append('E');
temp.append(decimalAt);
return Double.parseDouble(temp.toString());
}
/**
* Utility routine to get the value of the digit list.
* If (count == 0) this returns 0, unlike Long.parseLong().
*/
public final long getLong() {
// for now, simple implementation; later, do proper IEEE native stuff
if (count == 0) {
return 0;
}
// We have to check for this, because this is the one NEGATIVE value
// we represent. If we tried to just pass the digits off to parseLong,
// we'd get a parse failure.
if (isLongMIN_VALUE()) {
return Long.MIN_VALUE;
}
StringBuffer temp = getStringBuffer();
temp.append(digits, 0, count);
for (int i = count; i < decimalAt; ++i) {
temp.append('0');
}
return Long.parseLong(temp.toString());
}
public final BigDecimal getBigDecimal() {
if (count == 0) {
if (decimalAt == 0) {
return BigDecimal.ZERO;
} else {
return new BigDecimal("0E" + decimalAt);
}
}
if (decimalAt == count) {
return new BigDecimal(digits, 0, count);
} else {
return new BigDecimal(digits, 0, count).scaleByPowerOfTen(decimalAt - count);
}
}
/**
* Return true if the number represented by this object can fit into
* a long.
* @param isPositive true if this number should be regarded as positive
* @param ignoreNegativeZero true if -0 should be regarded as identical to
* +0; otherwise they are considered distinct
* @return true if this number fits into a Java long
*/
boolean fitsIntoLong(boolean isPositive, boolean ignoreNegativeZero) {
// Figure out if the result will fit in a long. We have to
// first look for nonzero digits after the decimal point;
// then check the size. If the digit count is 18 or less, then
// the value can definitely be represented as a long. If it is 19
// then it may be too large.
// Trim trailing zeros. This does not change the represented value.
while (count > 0 && digits[count - 1] == '0') {
--count;
}
if (count == 0) {
// Positive zero fits into a long, but negative zero can only
// be represented as a double. - bug 4162852
return isPositive || ignoreNegativeZero;
}
if (decimalAt < count || decimalAt > MAX_COUNT) {
return false;
}
if (decimalAt < MAX_COUNT) return true;
// At this point we have decimalAt == count, and count == MAX_COUNT.
// The number will overflow if it is larger than 9223372036854775807
// or smaller than -9223372036854775808.
for (int i=0; i<count; ++i) {
char dig = digits[i], max = LONG_MIN_REP[i];
if (dig > max) return false;
if (dig < max) return true;
}
// At this point the first count digits match. If decimalAt is less
// than count, then the remaining digits are zero, and we return true.
if (count < decimalAt) return true;
// Now we have a representation of Long.MIN_VALUE, without the leading
// negative sign. If this represents a positive value, then it does
// not fit; otherwise it fits.
return !isPositive;
}
/**
* Set the digit list to a representation of the given double value.
* This method supports fixed-point notation.
* @param isNegative Boolean value indicating whether the number is negative.
* @param source Value to be converted; must not be Inf, -Inf, Nan,
* or a value <= 0.
* @param maximumFractionDigits The most fractional digits which should
* be converted.
*/
final void set(boolean isNegative, double source, int maximumFractionDigits) {
set(isNegative, source, maximumFractionDigits, true);
}
/**
* Set the digit list to a representation of the given double value.
* This method supports both fixed-point and exponential notation.
* @param isNegative Boolean value indicating whether the number is negative.
* @param source Value to be converted; must not be Inf, -Inf, Nan,
* or a value <= 0.
* @param maximumDigits The most fractional or total digits which should
* be converted.
* @param fixedPoint If true, then maximumDigits is the maximum
* fractional digits to be converted. If false, total digits.
*/
final void set(boolean isNegative, double source, int maximumDigits, boolean fixedPoint) {
FloatingDecimal.BinaryToASCIIConverter fdConverter = FloatingDecimal.getBinaryToASCIIConverter(source);
boolean hasBeenRoundedUp = fdConverter.digitsRoundedUp();
boolean allDecimalDigits = fdConverter.decimalDigitsExact();
assert !fdConverter.isExceptional();
String digitsString = fdConverter.toJavaFormatString();
set(isNegative, digitsString,
hasBeenRoundedUp, allDecimalDigits,
maximumDigits, fixedPoint);
}
/**
* Generate a representation of the form DDDDD, DDDDD.DDDDD, or
* DDDDDE+/-DDDDD.
* @param roundedUp Boolean value indicating if the s digits were rounded-up.
* @param allDecimalDigits Boolean value indicating if the digits in s are
* an exact decimal representation of the double that was passed.
*/
private void set(boolean isNegative, String s,
boolean roundedUp, boolean allDecimalDigits,
int maximumDigits, boolean fixedPoint) {
this.isNegative = isNegative;
int len = s.length();
char[] source = getDataChars(len);
s.getChars(0, len, source, 0);
decimalAt = -1;
count = 0;
int exponent = 0;
// Number of zeros between decimal point and first non-zero digit after
// decimal point, for numbers < 1.
int leadingZerosAfterDecimal = 0;
boolean nonZeroDigitSeen = false;
for (int i = 0; i < len; ) {
char c = source[i++];
if (c == '.') {
decimalAt = count;
} else if (c == 'e' || c == 'E') {
exponent = parseInt(source, i, len);
break;
} else {
if (!nonZeroDigitSeen) {
nonZeroDigitSeen = (c != '0');
if (!nonZeroDigitSeen && decimalAt != -1)
++leadingZerosAfterDecimal;
}
if (nonZeroDigitSeen) {
digits[count++] = c;
}
}
}
if (decimalAt == -1) {
decimalAt = count;
}
if (nonZeroDigitSeen) {
decimalAt += exponent - leadingZerosAfterDecimal;
}
if (fixedPoint) {
// The negative of the exponent represents the number of leading
// zeros between the decimal and the first non-zero digit, for
// a value < 0.1 (e.g., for 0.00123, -decimalAt == 2). If this
// is more than the maximum fraction digits, then we have an underflow
// for the printed representation.
if (-decimalAt > maximumDigits) {
// Handle an underflow to zero when we round something like
// 0.0009 to 2 fractional digits.
count = 0;
return;
} else if (-decimalAt == maximumDigits) {
// If we round 0.0009 to 3 fractional digits, then we have to
// create a new one digit in the least significant location.
if (shouldRoundUp(0, roundedUp, allDecimalDigits)) {
count = 1;
++decimalAt;
digits[0] = '1';
} else {
count = 0;
}
return;
}
// else fall through
}
// Eliminate trailing zeros.
while (count > 1 && digits[count - 1] == '0') {
--count;
}
// Eliminate digits beyond maximum digits to be displayed.
// Round up if appropriate.
round(fixedPoint ? (maximumDigits + decimalAt) : maximumDigits,
roundedUp, allDecimalDigits);
}
/**
* Round the representation to the given number of digits.
* @param maximumDigits The maximum number of digits to be shown.
* @param alreadyRounded Boolean indicating if rounding up already happened.
* @param allDecimalDigits Boolean indicating if the digits provide an exact
* representation of the value.
*
* Upon return, count will be less than or equal to maximumDigits.
*/
private final void round(int maximumDigits,
boolean alreadyRounded,
boolean allDecimalDigits) {
// Eliminate digits beyond maximum digits to be displayed.
// Round up if appropriate.
if (maximumDigits >= 0 && maximumDigits < count) {
if (shouldRoundUp(maximumDigits, alreadyRounded, allDecimalDigits)) {
// Rounding up involved incrementing digits from LSD to MSD.
// In most cases this is simple, but in a worst case situation
// (9999..99) we have to adjust the decimalAt value.
for (;;) {
--maximumDigits;
if (maximumDigits < 0) {
// We have all 9's, so we increment to a single digit
// of one and adjust the exponent.
digits[0] = '1';
++decimalAt;
maximumDigits = 0; // Adjust the count
break;
}
++digits[maximumDigits];
if (digits[maximumDigits] <= '9') break;
// digits[maximumDigits] = '0'; // Unnecessary since we'll truncate this
}
++maximumDigits; // Increment for use as count
}
count = maximumDigits;
// Eliminate trailing zeros.
while (count > 1 && digits[count-1] == '0') {
--count;
}
}
}
/**
* Return true if truncating the representation to the given number
* of digits will result in an increment to the last digit. This
* method implements the rounding modes defined in the
* java.math.RoundingMode class.
* [bnf]
* @param maximumDigits the number of digits to keep, from 0 to
* <code>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 "#.#").
* @exception ArithmeticException if rounding is needed with rounding
* mode being set to RoundingMode.UNNECESSARY
* @return true if digit <code>maximumDigits-1 should be
* incremented
*/
private boolean shouldRoundUp(int maximumDigits,
boolean alreadyRounded,
boolean allDecimalDigits) {
if (maximumDigits < count) {
/*
* To avoid erroneous double-rounding or truncation when converting
* a binary double value to text, information about the exactness
* of the conversion result in FloatingDecimal, as well as any
* rounding done, is needed in this class.
*
* - For the HALF_DOWN, HALF_EVEN, HALF_UP rounding rules below:
* In the case of formating float or double, We must take into
* account what FloatingDecimal has done in the binary to decimal
* conversion.
*
* Considering the tie cases, FloatingDecimal may round-up the
* value (returning decimal digits equal to tie when it is below),
* or "truncate" the value to the tie while value is above it,
* or provide the exact decimal digits when the binary value can be
* converted exactly to its decimal representation given formating
* rules of FloatingDecimal ( we have thus an exact decimal
* representation of the binary value).
*
* - If the double binary value was converted exactly as a decimal
* value, then DigitList code must apply the expected rounding
* rule.
*
* - If FloatingDecimal already rounded up the decimal value,
* DigitList should neither round up the value again in any of
* the three rounding modes above.
*
* - If FloatingDecimal has truncated the decimal value to
* an ending '5' digit, DigitList should round up the value in
* all of the three rounding modes above.
*
*
* This has to be considered only if digit at maximumDigits index
* is exactly the last one in the set of digits, otherwise there are
* remaining digits after that position and we don't have to consider
* what FloatingDecimal did.
*
* - Other rounding modes are not impacted by these tie cases.
*
* - For other numbers that are always converted to exact digits
* (like BigInteger, Long, ...), the passed alreadyRounded boolean
* have to be set to false, and allDecimalDigits has to be set to
* true in the upper DigitList call stack, providing the right state
* for those situations..
*/
switch(roundingMode) {
case UP:
for (int i=maximumDigits; i<count; ++i) {
if (digits[i] != '0') {
return true;
}
}
break;
case DOWN:
break;
case CEILING:
for (int i=maximumDigits; i<count; ++i) {
if (digits[i] != '0') {
return !isNegative;
}
}
break;
case FLOOR:
for (int i=maximumDigits; i<count; ++i) {
if (digits[i] != '0') {
return isNegative;
}
}
break;
case HALF_UP:
if (digits[maximumDigits] >= '5') {
// We should not round up if the rounding digits position is
// exactly the last index and if digits were already rounded.
if ((maximumDigits == (count - 1)) &&
(alreadyRounded))
return false;
// Value was exactly at or was above tie. We must round up.
return true;
}
break;
case HALF_DOWN:
if (digits[maximumDigits] > '5') {
return true;
} else if (digits[maximumDigits] == '5' ) {
if (maximumDigits == (count - 1)) {
// The rounding position is exactly the last index.
if (allDecimalDigits || alreadyRounded)
/* FloatingDecimal rounded up (value was below tie),
* or provided the exact list of digits (value was
* an exact tie). We should not round up, following
* the HALF_DOWN rounding rule.
*/
return false;
else
// Value was above the tie, we must round up.
return true;
}
// We must round up if it gives a non null digit after '5'.
for (int i=maximumDigits+1; i<count; ++i) {
if (digits[i] != '0') {
return true;
}
}
}
break;
case HALF_EVEN:
// Implement IEEE half-even rounding
if (digits[maximumDigits] > '5') {
return true;
} else if (digits[maximumDigits] == '5' ) {
if (maximumDigits == (count - 1)) {
// the rounding position is exactly the last index :
if (alreadyRounded)
// If FloatingDecimal rounded up (value was below tie),
// then we should not round up again.
return false;
if (!allDecimalDigits)
// Otherwise if the digits don't represent exact value,
// value was above tie and FloatingDecimal truncated
// digits to tie. We must round up.
return true;
else {
// This is an exact tie value, and FloatingDecimal
// provided all of the exact digits. We thus apply
// HALF_EVEN rounding rule.
return ((maximumDigits > 0) &&
(digits[maximumDigits-1] % 2 != 0));
}
} else {
// Rounds up if it gives a non null digit after '5'
for (int i=maximumDigits+1; i<count; ++i) {
if (digits[i] != '0')
return true;
}
}
}
break;
case UNNECESSARY:
for (int i=maximumDigits; i<count; ++i) {
if (digits[i] != '0') {
throw new ArithmeticException(
"Rounding needed with the rounding mode being set to RoundingMode.UNNECESSARY");
}
}
break;
default:
assert false;
}
}
return false;
}
/**
* Utility routine to set the value of the digit list from a long
*/
final void set(boolean isNegative, long source) {
set(isNegative, source, 0);
}
/**
* Set the digit list to a representation of the given long value.
* @param isNegative Boolean value indicating whether the number is negative.
* @param source Value to be converted; must be >= 0 or ==
* Long.MIN_VALUE.
* @param 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.
*/
final void set(boolean isNegative, long source, int maximumDigits) {
this.isNegative = isNegative;
// This method does not expect a negative number. However,
// "source" can be a Long.MIN_VALUE (-9223372036854775808),
// if the number being formatted is a Long.MIN_VALUE. In that
// case, it will be formatted as -Long.MIN_VALUE, a number
// which is outside the legal range of a long, but which can
// be represented by DigitList.
if (source <= 0) {
if (source == Long.MIN_VALUE) {
decimalAt = count = MAX_COUNT;
System.arraycopy(LONG_MIN_REP, 0, digits, 0, count);
} else {
decimalAt = count = 0; // Values <= 0 format as zero
}
} else {
// Rewritten to improve performance. I used to call
// Long.toString(), which was about 4x slower than this code.
int left = MAX_COUNT;
int right;
while (source > 0) {
digits[--left] = (char)('0' + (source % 10));
source /= 10;
}
decimalAt = MAX_COUNT - left;
// Don't copy trailing zeros. We are guaranteed that there is at
// least one non-zero digit, so we don't have to check lower bounds.
for (right = MAX_COUNT - 1; digits[right] == '0'; --right)
;
count = right - left + 1;
System.arraycopy(digits, left, digits, 0, count);
}
if (maximumDigits > 0) round(maximumDigits, false, true);
}
/**
* Set the digit list to a representation of the given BigDecimal value.
* This method supports both fixed-point and exponential notation.
* @param isNegative Boolean value indicating whether the number is negative.
* @param source Value to be converted; must not be a value <= 0.
* @param maximumDigits The most fractional or total digits which should
* be converted.
* @param fixedPoint If true, then maximumDigits is the maximum
* fractional digits to be converted. If false, total digits.
*/
final void set(boolean isNegative, BigDecimal source, int maximumDigits, boolean fixedPoint) {
String s = source.toString();
extendDigits(s.length());
set(isNegative, s,
false, true,
maximumDigits, fixedPoint);
}
/**
* Set the digit list to a representation of the given BigInteger value.
* @param isNegative Boolean value indicating whether the number is negative.
* @param source Value to be converted; must be >= 0.
* @param 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.
*/
final void set(boolean isNegative, BigInteger source, int maximumDigits) {
this.isNegative = isNegative;
String s = source.toString();
int len = s.length();
extendDigits(len);
s.getChars(0, len, digits, 0);
decimalAt = len;
int right;
for (right = len - 1; right >= 0 && digits[right] == '0'; --right)
;
count = right + 1;
if (maximumDigits > 0) {
round(maximumDigits, false, true);
}
}
/**
* equality test between two digit lists.
*/
public boolean equals(Object obj) {
if (this == obj) // quick check
return true;
if (!(obj instanceof DigitList)) // (1) same object?
return false;
DigitList other = (DigitList) obj;
if (count != other.count ||
decimalAt != other.decimalAt)
return false;
for (int i = 0; i < count; i++)
if (digits[i] != other.digits[i])
return false;
return true;
}
/**
* Generates the hash code for the digit list.
*/
public int hashCode() {
int hashcode = decimalAt;
for (int i = 0; i < count; i++) {
hashcode = hashcode * 37 + digits[i];
}
return hashcode;
}
/**
* Creates a copy of this object.
* @return a clone of this instance.
*/
public Object clone() {
try {
DigitList other = (DigitList) super.clone();
char[] newDigits = new char[digits.length];
System.arraycopy(digits, 0, newDigits, 0, digits.length);
other.digits = newDigits;
other.tempBuffer = null;
return other;
} catch (CloneNotSupportedException e) {
throw new InternalError(e);
}
}
/**
* Returns true if this DigitList represents Long.MIN_VALUE;
* false, otherwise. This is required so that getLong() works.
*/
private boolean isLongMIN_VALUE() {
if (decimalAt != count || count != MAX_COUNT) {
return false;
}
for (int i = 0; i < count; ++i) {
if (digits[i] != LONG_MIN_REP[i]) return false;
}
return true;
}
private static final int parseInt(char[] str, int offset, int strLen) {
char c;
boolean positive = true;
if ((c = str[offset]) == '-') {
positive = false;
offset++;
} else if (c == '+') {
offset++;
}
int value = 0;
while (offset < strLen) {
c = str[offset++];
if (c >= '0' && c <= '9') {
value = value * 10 + (c - '0');
} else {
break;
}
}
return positive ? value : -value;
}
// The digit part of -9223372036854775808L
private static final char[] LONG_MIN_REP = "9223372036854775808".toCharArray();
public String toString() {
if (isZero()) {
return "0";
}
StringBuffer buf = getStringBuffer();
buf.append("0.");
buf.append(digits, 0, count);
buf.append("x10^");
buf.append(decimalAt);
return buf.toString();
}
private StringBuffer tempBuffer;
private StringBuffer getStringBuffer() {
if (tempBuffer == null) {
tempBuffer = new StringBuffer(MAX_COUNT);
} else {
tempBuffer.setLength(0);
}
return tempBuffer;
}
private void extendDigits(int len) {
if (len > digits.length) {
digits = new char[len];
}
}
private final char[] getDataChars(int length) {
if (data == null || data.length < length) {
data = new char[length];
}
return data;
}
}
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