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Java example source code file (BigFractionFormat.java)

This example Java source code file (BigFractionFormat.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

abstractformat, bigfraction, bigfractionformat, biginteger, fieldposition, locale, math, mathparseexception, numberformat, numberformatexception, override, parseposition, properbigfractionformat, serializable, stringbuffer, text, util

The BigFractionFormat.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.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.
 * <p>
 * The number format for each of the whole number, numerator and,
 * denominator can be configured.
 * </p>
 *
 * @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.
     * <code>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 <code>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 <code>BigInteger.
     * @param source the string to parse
     * @param pos input/output parsing parameter.
     * @return a parsed <code>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;
         }

    }

}

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