org.apache.commons.math.fraction.FractionFormat Maven / Gradle / Ivy
/*
* 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.math.fraction;
import java.io.Serializable;
import java.text.FieldPosition;
import java.text.Format;
import java.text.NumberFormat;
import java.text.ParseException;
import java.text.ParsePosition;
import java.util.Locale;
import org.apache.commons.math.ConvergenceException;
/**
* 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
* @version $Revision: 506713 $ $Date: 2007-02-12 15:35:08 -0700 (Mon, 12 Feb 2007) $
*/
public class FractionFormat extends Format implements Serializable {
/** Serializable version identifier */
private static final long serialVersionUID = -6337346779577272306L;
/** The format used for the denominator. */
private NumberFormat denominatorFormat;
/** The format used for the numerator. */
private NumberFormat numeratorFormat;
/**
* Create an improper formatting instance with the default number format
* for the numerator and denominator.
*/
public FractionFormat() {
this(getDefaultNumberFormat());
}
/**
* 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(NumberFormat format) {
this(format, (NumberFormat)format.clone());
}
/**
* 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(NumberFormat numeratorFormat,
NumberFormat denominatorFormat)
{
super();
this.numeratorFormat = numeratorFormat;
this.denominatorFormat = denominatorFormat;
}
/**
* 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);
}
/**
* 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();
}
/**
* 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(Locale locale) {
NumberFormat f = getDefaultNumberFormat(locale);
return new FractionFormat(f);
}
/**
* 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(Locale locale) {
NumberFormat f = getDefaultNumberFormat(locale);
return new ProperFractionFormat(f);
}
/**
* 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());
}
/**
* 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.
* @param locale the specific locale used by the format.
* @return the default number format specific to the given locale.
*/
private static NumberFormat getDefaultNumberFormat(Locale locale) {
NumberFormat nf = NumberFormat.getNumberInstance(locale);
nf.setMaximumFractionDigits(0);
nf.setParseIntegerOnly(true);
return nf;
}
/**
* 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(Fraction fraction, StringBuffer toAppendTo,
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 a object to produce a string. 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 IllegalArgumentException is obj is not a valid type.
*/
public StringBuffer format(Object obj, StringBuffer toAppendTo,
FieldPosition pos)
{
StringBuffer ret = null;
if (obj instanceof Fraction) {
ret = format( (Fraction)obj, toAppendTo, pos);
} else if (obj instanceof Number) {
try {
ret = format( new Fraction(((Number)obj).doubleValue()),
toAppendTo, pos);
} catch (ConvergenceException ex) {
throw new IllegalArgumentException(
"Cannot convert given object to a fraction.");
}
} else {
throw new IllegalArgumentException(
"Cannot format given object as a fraction");
}
return ret;
}
/**
* Access the denominator format.
* @return the denominator format.
*/
public NumberFormat getDenominatorFormat() {
return denominatorFormat;
}
/**
* Access the numerator format.
* @return the numerator format.
*/
public NumberFormat getNumeratorFormat() {
return numeratorFormat;
}
/**
* Parses a string to produce a {@link Fraction} object.
* @param source the string to parse
* @return the parsed {@link Fraction} object.
* @exception ParseException if the beginning of the specified string
* cannot be parsed.
*/
public Fraction parse(String source) throws ParseException {
ParsePosition parsePosition = new ParsePosition(0);
Fraction result = parse(source, parsePosition);
if (parsePosition.getIndex() == 0) {
throw new ParseException("Unparseable fraction number: \"" +
source + "\"", parsePosition.getErrorIndex());
}
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/ouput parsing parameter.
* @return the parsed {@link Fraction} object.
*/
public Fraction parse(String source, ParsePosition pos) {
int initialIndex = pos.getIndex();
// parse whitespace
parseAndIgnoreWhitespace(source, pos);
// parse numerator
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 '/'
int startIndex = pos.getIndex();
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
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());
}
/**
* Parses a string to produce a object.
* @param source the string to parse
* @param pos input/ouput parsing parameter.
* @return the parsed object.
* @see java.text.Format#parseObject(java.lang.String, java.text.ParsePosition)
*/
public Object parseObject(String source, ParsePosition pos) {
return parse(source, pos);
}
/**
* Modify the denominator format.
* @param format the new denominator format value.
* @throws IllegalArgumentException if format is
* null.
*/
public void setDenominatorFormat(NumberFormat format) {
if (format == null) {
throw new IllegalArgumentException(
"denominator format can not be null.");
}
this.denominatorFormat = format;
}
/**
* Modify the numerator format.
* @param format the new numerator format value.
* @throws IllegalArgumentException if format is
* null.
*/
public void setNumeratorFormat(NumberFormat format) {
if (format == null) {
throw new IllegalArgumentException(
"numerator format can not be null.");
}
this.numeratorFormat = format;
}
/**
* Parses source until a non-whitespace character is found.
* @param source the string to parse
* @param pos input/ouput parsing parameter. On output, pos
* holds the index of the next non-whitespace character.
*/
protected static void parseAndIgnoreWhitespace(
String source, ParsePosition pos)
{
parseNextCharacter(source, pos);
pos.setIndex(pos.getIndex() - 1);
}
/**
* Parses source until a non-whitespace character is found.
* @param source the string to parse
* @param pos input/ouput parsing parameter.
* @return the first non-whitespace character.
*/
protected static char parseNextCharacter(String source, ParsePosition pos) {
int index = pos.getIndex();
int n = source.length();
char ret = 0;
if (index < n) {
char c;
do {
c = source.charAt(index++);
} while (Character.isWhitespace(c) && index < n);
pos.setIndex(index);
if (index < n) {
ret = c;
}
}
return ret;
}
}
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