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With inspiration from other libraries
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.math3.fraction;
import java.math.BigInteger;
import java.text.FieldPosition;
import java.text.NumberFormat;
import java.text.ParsePosition;
import org.apache.commons.math3.exception.util.LocalizedFormats;
import org.apache.commons.math3.exception.NullArgumentException;
/**
* Formats a BigFraction number in proper format. The number format for each of
* the whole number, numerator and, denominator can be configured.
*
* Minus signs are only allowed in the whole number part - i.e.,
* "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
* will result in a ParseException.
*
* @since 1.1
*/
public class ProperBigFractionFormat extends BigFractionFormat {
/** Serializable version identifier */
private static final long serialVersionUID = -6337346779577272307L;
/** The format used for the whole number. */
private NumberFormat wholeFormat;
/**
* Create a proper formatting instance with the default number format for
* the whole, numerator, and denominator.
*/
public ProperBigFractionFormat() {
this(getDefaultNumberFormat());
}
/**
* Create a proper formatting instance with a custom number format for the
* whole, numerator, and denominator.
* @param format the custom format for the whole, numerator, and
* denominator.
*/
public ProperBigFractionFormat(final NumberFormat format) {
this(format, (NumberFormat)format.clone(), (NumberFormat)format.clone());
}
/**
* Create a proper formatting instance with a custom number format for each
* of the whole, numerator, and denominator.
* @param wholeFormat the custom format for the whole.
* @param numeratorFormat the custom format for the numerator.
* @param denominatorFormat the custom format for the denominator.
*/
public ProperBigFractionFormat(final NumberFormat wholeFormat,
final NumberFormat numeratorFormat,
final NumberFormat denominatorFormat) {
super(numeratorFormat, denominatorFormat);
setWholeFormat(wholeFormat);
}
/**
* Formats a {@link BigFraction} object to produce a string. The BigFraction
* is output in proper format.
*
* @param fraction the object to format.
* @param toAppendTo where the text is to be appended
* @param pos On input: an alignment field, if desired. On output: the
* offsets of the alignment field
* @return the value passed in as toAppendTo.
*/
@Override
public StringBuffer format(final BigFraction fraction,
final StringBuffer toAppendTo, final FieldPosition pos) {
pos.setBeginIndex(0);
pos.setEndIndex(0);
BigInteger num = fraction.getNumerator();
BigInteger den = fraction.getDenominator();
BigInteger whole = num.divide(den);
num = num.remainder(den);
if (!BigInteger.ZERO.equals(whole)) {
getWholeFormat().format(whole, toAppendTo, pos);
toAppendTo.append(' ');
if (num.compareTo(BigInteger.ZERO) < 0) {
num = num.negate();
}
}
getNumeratorFormat().format(num, toAppendTo, pos);
toAppendTo.append(" / ");
getDenominatorFormat().format(den, toAppendTo, pos);
return toAppendTo;
}
/**
* Access the whole format.
* @return the whole format.
*/
public NumberFormat getWholeFormat() {
return wholeFormat;
}
/**
* Parses a string to produce a {@link BigFraction} object. This method
* expects the string to be formatted as a proper BigFraction.
*
* Minus signs are only allowed in the whole number part - i.e.,
* "-3 1/2" is legitimate and denotes -7/2, but "-3 -1/2" is invalid and
* will result in a ParseException.
*
* @param source the string to parse
* @param pos input/ouput parsing parameter.
* @return the parsed {@link BigFraction} object.
*/
@Override
public BigFraction parse(final String source, final ParsePosition pos) {
// try to parse improper BigFraction
BigFraction ret = super.parse(source, pos);
if (ret != null) {
return ret;
}
final int initialIndex = pos.getIndex();
// parse whitespace
parseAndIgnoreWhitespace(source, pos);
// parse whole
BigInteger whole = parseNextBigInteger(source, pos);
if (whole == null) {
// invalid integer number
// set index back to initial, error index should already be set
// character examined.
pos.setIndex(initialIndex);
return null;
}
// parse whitespace
parseAndIgnoreWhitespace(source, pos);
// parse numerator
BigInteger num = parseNextBigInteger(source, pos);
if (num == null) {
// invalid integer number
// set index back to initial, error index should already be set
// character examined.
pos.setIndex(initialIndex);
return null;
}
if (num.compareTo(BigInteger.ZERO) < 0) {
// minus signs should be leading, invalid expression
pos.setIndex(initialIndex);
return null;
}
// parse '/'
final int startIndex = pos.getIndex();
final char c = parseNextCharacter(source, pos);
switch (c) {
case 0 :
// no '/'
// return num as a BigFraction
return new BigFraction(num);
case '/' :
// found '/', continue parsing denominator
break;
default :
// invalid '/'
// set index back to initial, error index should be the last
// character examined.
pos.setIndex(initialIndex);
pos.setErrorIndex(startIndex);
return null;
}
// parse whitespace
parseAndIgnoreWhitespace(source, pos);
// parse denominator
final BigInteger den = parseNextBigInteger(source, pos);
if (den == null) {
// invalid integer number
// set index back to initial, error index should already be set
// character examined.
pos.setIndex(initialIndex);
return null;
}
if (den.compareTo(BigInteger.ZERO) < 0) {
// minus signs must be leading, invalid
pos.setIndex(initialIndex);
return null;
}
boolean wholeIsNeg = whole.compareTo(BigInteger.ZERO) < 0;
if (wholeIsNeg) {
whole = whole.negate();
}
num = whole.multiply(den).add(num);
if (wholeIsNeg) {
num = num.negate();
}
return new BigFraction(num, den);
}
/**
* Modify the whole format.
* @param format The new whole format value.
* @throws NullArgumentException if {@code format} is {@code null}.
*/
public void setWholeFormat(final NumberFormat format) {
if (format == null) {
throw new NullArgumentException(LocalizedFormats.WHOLE_FORMAT);
}
this.wholeFormat = format;
}
}