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Java example source code file (ProperFractionFormat.java)

This example Java source code file (ProperFractionFormat.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

fieldposition, fraction, number, numberformat, override, parseposition, properfractionformat, stringbuffer, text

The ProperFractionFormat.java Java example source code

/*
 * 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 org.apache.commons.math3.exception.util.LocalizedFormats;
import org.apache.commons.math3.exception.NullArgumentException;
import org.apache.commons.math3.util.FastMath;
import org.apache.commons.math3.util.MathUtils;

/**
 * Formats a Fraction number in proper format.  The number format for each of
 * the whole number, numerator and, denominator can be configured.
 * <p>
 * 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 <code>ParseException.

* * @since 1.1 */ public class ProperFractionFormat extends FractionFormat { /** Serializable version identifier */ private static final long serialVersionUID = 760934726031766749L; /** 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 ProperFractionFormat() { 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 ProperFractionFormat(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 ProperFractionFormat(NumberFormat wholeFormat, NumberFormat numeratorFormat, NumberFormat denominatorFormat) { super(numeratorFormat, denominatorFormat); setWholeFormat(wholeFormat); } /** * Formats a {@link Fraction} object to produce a string. The fraction * 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(Fraction fraction, StringBuffer toAppendTo, FieldPosition pos) { pos.setBeginIndex(0); pos.setEndIndex(0); int num = fraction.getNumerator(); int den = fraction.getDenominator(); int whole = num / den; num %= den; if (whole != 0) { getWholeFormat().format(whole, toAppendTo, pos); toAppendTo.append(' '); num = FastMath.abs(num); } 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 Fraction} object. This method * expects the string to be formatted as a proper fraction. * <p> * 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 <code>ParseException.

* * @param source the string to parse * @param pos input/ouput parsing parameter. * @return the parsed {@link Fraction} object. */ @Override public Fraction parse(String source, ParsePosition pos) { // try to parse improper fraction Fraction ret = super.parse(source, pos); if (ret != null) { return ret; } int initialIndex = pos.getIndex(); // parse whitespace parseAndIgnoreWhitespace(source, pos); // parse whole Number whole = getWholeFormat().parse(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 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; } if (num.intValue() < 0) { // minus signs should be leading, invalid expression 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; } if (den.intValue() < 0) { // minus signs must be leading, invalid pos.setIndex(initialIndex); return null; } int w = whole.intValue(); int n = num.intValue(); int d = den.intValue(); return new Fraction(((FastMath.abs(w) * d) + n) * MathUtils.copySign(1, w), d); } /** * Modify the whole format. * @param format The new whole format value. * @throws NullArgumentException if {@code format} is {@code null}. */ public void setWholeFormat(NumberFormat format) { if (format == null) { throw new NullArgumentException(LocalizedFormats.WHOLE_FORMAT); } this.wholeFormat = format; } }

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