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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.io.Serializable;
import java.math.BigInteger;
import java.text.FieldPosition;
import java.text.NumberFormat;
import java.text.ParsePosition;
import java.util.Locale;
import org.apache.commons.math3.exception.MathIllegalArgumentException;
import org.apache.commons.math3.exception.MathParseException;
import org.apache.commons.math3.exception.util.LocalizedFormats;
/**
* Formats a BigFraction number in proper format or improper format.
*
* The number format for each of the whole number, numerator and,
* denominator can be configured.
*
*
* @since 2.0
*/
public class BigFractionFormat extends AbstractFormat implements Serializable {
/** Serializable version identifier */
private static final long serialVersionUID = -2932167925527338976L;
/**
* Create an improper formatting instance with the default number format
* for the numerator and denominator.
*/
public BigFractionFormat() {
}
/**
* Create an improper formatting instance with a custom number format for
* both the numerator and denominator.
* @param format the custom format for both the numerator and denominator.
*/
public BigFractionFormat(final NumberFormat format) {
super(format);
}
/**
* Create an improper formatting instance with a custom number format for
* the numerator and a custom number format for the denominator.
* @param numeratorFormat the custom format for the numerator.
* @param denominatorFormat the custom format for the denominator.
*/
public BigFractionFormat(final NumberFormat numeratorFormat,
final NumberFormat denominatorFormat) {
super(numeratorFormat, denominatorFormat);
}
/**
* Get the set of locales for which complex formats are available. This
* is the same set as the {@link NumberFormat} set.
* @return available complex format locales.
*/
public static Locale[] getAvailableLocales() {
return NumberFormat.getAvailableLocales();
}
/**
* This static method calls formatBigFraction() on a default instance of
* BigFractionFormat.
*
* @param f BigFraction object to format
* @return A formatted BigFraction in proper form.
*/
public static String formatBigFraction(final BigFraction f) {
return getImproperInstance().format(f);
}
/**
* Returns the default complex format for the current locale.
* @return the default complex format.
*/
public static BigFractionFormat getImproperInstance() {
return getImproperInstance(Locale.getDefault());
}
/**
* Returns the default complex format for the given locale.
* @param locale the specific locale used by the format.
* @return the complex format specific to the given locale.
*/
public static BigFractionFormat getImproperInstance(final Locale locale) {
return new BigFractionFormat(getDefaultNumberFormat(locale));
}
/**
* Returns the default complex format for the current locale.
* @return the default complex format.
*/
public static BigFractionFormat getProperInstance() {
return getProperInstance(Locale.getDefault());
}
/**
* Returns the default complex format for the given locale.
* @param locale the specific locale used by the format.
* @return the complex format specific to the given locale.
*/
public static BigFractionFormat getProperInstance(final Locale locale) {
return new ProperBigFractionFormat(getDefaultNumberFormat(locale));
}
/**
* Formats a {@link BigFraction} object to produce a string. The BigFraction is
* output in improper format.
*
* @param BigFraction 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.
*/
public StringBuffer format(final BigFraction BigFraction,
final StringBuffer toAppendTo, final FieldPosition pos) {
pos.setBeginIndex(0);
pos.setEndIndex(0);
getNumeratorFormat().format(BigFraction.getNumerator(), toAppendTo, pos);
toAppendTo.append(" / ");
getDenominatorFormat().format(BigFraction.getDenominator(), toAppendTo, pos);
return toAppendTo;
}
/**
* Formats an object and appends the result to a StringBuffer.
* obj must be either a {@link BigFraction} object or a
* {@link BigInteger} object or a {@link Number} object. Any other type of
* object will result in an {@link IllegalArgumentException} being thrown.
*
* @param obj 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.
* @see java.text.Format#format(java.lang.Object, java.lang.StringBuffer, java.text.FieldPosition)
* @throws MathIllegalArgumentException if obj is not a valid type.
*/
@Override
public StringBuffer format(final Object obj,
final StringBuffer toAppendTo, final FieldPosition pos) {
final StringBuffer ret;
if (obj instanceof BigFraction) {
ret = format((BigFraction) obj, toAppendTo, pos);
} else if (obj instanceof BigInteger) {
ret = format(new BigFraction((BigInteger) obj), toAppendTo, pos);
} else if (obj instanceof Number) {
ret = format(new BigFraction(((Number) obj).doubleValue()),
toAppendTo, pos);
} else {
throw new MathIllegalArgumentException(LocalizedFormats.CANNOT_FORMAT_OBJECT_TO_FRACTION);
}
return ret;
}
/**
* Parses a string to produce a {@link BigFraction} object.
* @param source the string to parse
* @return the parsed {@link BigFraction} object.
* @exception MathParseException if the beginning of the specified string
* cannot be parsed.
*/
@Override
public BigFraction parse(final String source) throws MathParseException {
final ParsePosition parsePosition = new ParsePosition(0);
final BigFraction result = parse(source, parsePosition);
if (parsePosition.getIndex() == 0) {
throw new MathParseException(source, parsePosition.getErrorIndex(), BigFraction.class);
}
return result;
}
/**
* Parses a string to produce a {@link BigFraction} object.
* This method expects the string to be formatted as an improper BigFraction.
* @param source the string to parse
* @param pos input/output parsing parameter.
* @return the parsed {@link BigFraction} object.
*/
@Override
public BigFraction parse(final String source, final ParsePosition pos) {
final int initialIndex = pos.getIndex();
// parse whitespace
parseAndIgnoreWhitespace(source, pos);
// parse numerator
final 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;
}
// 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;
}
return new BigFraction(num, den);
}
/**
* Parses a string to produce a BigInteger.
* @param source the string to parse
* @param pos input/output parsing parameter.
* @return a parsed BigInteger or null if string does not
* contain a BigInteger at the specified position
*/
protected BigInteger parseNextBigInteger(final String source,
final ParsePosition pos) {
final int start = pos.getIndex();
int end = (source.charAt(start) == '-') ? (start + 1) : start;
while((end < source.length()) &&
Character.isDigit(source.charAt(end))) {
++end;
}
try {
BigInteger n = new BigInteger(source.substring(start, end));
pos.setIndex(end);
return n;
} catch (NumberFormatException nfe) {
pos.setErrorIndex(start);
return null;
}
}
}