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The Apache Commons Math project is a library of lightweight, self-contained mathematics and statistics components addressing the most common practical problems not immediately available in the Java programming language or commons-lang.
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/*
* 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.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 Fraction number in proper format or improper format. The number
* format for each of the whole number, numerator and, denominator can be
* configured.
*
* @since 1.1
*/
public class FractionFormat extends AbstractFormat {
/** Serializable version identifier */
private static final long serialVersionUID = 3008655719530972611L;
/**
* Create an improper formatting instance with the default number format
* for the numerator and denominator.
*/
public FractionFormat() {
}
/**
* 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 FractionFormat(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 FractionFormat(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 formatFraction() on a default instance of
* FractionFormat.
*
* @param f Fraction object to format
* @return a formatted fraction in proper form.
*/
public static String formatFraction(Fraction f) {
return getImproperInstance().format(f);
}
/**
* Returns the default complex format for the current locale.
* @return the default complex format.
*/
public static FractionFormat 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 FractionFormat getImproperInstance(final Locale locale) {
return new FractionFormat(getDefaultNumberFormat(locale));
}
/**
* Returns the default complex format for the current locale.
* @return the default complex format.
*/
public static FractionFormat 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 FractionFormat getProperInstance(final Locale locale) {
return new ProperFractionFormat(getDefaultNumberFormat(locale));
}
/**
* Create a default number format. The default number format is based on
* {@link NumberFormat#getNumberInstance(java.util.Locale)} with the only
* customizing is the maximum number of fraction digits, which is set to 0.
* @return the default number format.
*/
protected static NumberFormat getDefaultNumberFormat() {
return getDefaultNumberFormat(Locale.getDefault());
}
/**
* Formats a {@link Fraction} object to produce a string. The fraction is
* output in improper 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.
*/
public StringBuffer format(final Fraction fraction,
final StringBuffer toAppendTo, final FieldPosition pos) {
pos.setBeginIndex(0);
pos.setEndIndex(0);
getNumeratorFormat().format(fraction.getNumerator(), toAppendTo, pos);
toAppendTo.append(" / ");
getDenominatorFormat().format(fraction.getDenominator(), toAppendTo,
pos);
return toAppendTo;
}
/**
* Formats an object and appends the result to a StringBuffer. obj must be either a
* {@link Fraction} 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 FractionConversionException if the number cannot be converted to a fraction
* @throws MathIllegalArgumentException if obj is not a valid type.
*/
@Override
public StringBuffer format(final Object obj,
final StringBuffer toAppendTo, final FieldPosition pos)
throws FractionConversionException, MathIllegalArgumentException {
StringBuffer ret = null;
if (obj instanceof Fraction) {
ret = format((Fraction) obj, toAppendTo, pos);
} else if (obj instanceof Number) {
ret = format(new Fraction(((Number) obj).doubleValue()), toAppendTo, pos);
} else {
throw new MathIllegalArgumentException(LocalizedFormats.CANNOT_FORMAT_OBJECT_TO_FRACTION);
}
return ret;
}
/**
* Parses a string to produce a {@link Fraction} object.
* @param source the string to parse
* @return the parsed {@link Fraction} object.
* @exception MathParseException if the beginning of the specified string
* cannot be parsed.
*/
@Override
public Fraction parse(final String source) throws MathParseException {
final ParsePosition parsePosition = new ParsePosition(0);
final Fraction result = parse(source, parsePosition);
if (parsePosition.getIndex() == 0) {
throw new MathParseException(source, parsePosition.getErrorIndex(), Fraction.class);
}
return result;
}
/**
* Parses a string to produce a {@link Fraction} object. This method
* expects the string to be formatted as an improper fraction.
* @param source the string to parse
* @param pos input/output parsing parameter.
* @return the parsed {@link Fraction} object.
*/
@Override
public Fraction parse(final String source, final ParsePosition pos) {
final int initialIndex = pos.getIndex();
// parse whitespace
parseAndIgnoreWhitespace(source, pos);
// parse numerator
final Number num = getNumeratorFormat().parse(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 fraction
return new Fraction(num.intValue(), 1);
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 Number den = getDenominatorFormat().parse(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 Fraction(num.intValue(), den.intValue());
}
}