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Java example source code file (CompositeFormat.java)

This example Java source code file (CompositeFormat.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

compositeformat, fieldposition, locale, number, numberformat, parseposition, string, stringbuffer, stringbuilder, text, util

The CompositeFormat.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.util;

import java.text.FieldPosition;
import java.text.NumberFormat;
import java.text.ParsePosition;
import java.util.Locale;

/**
 * Base class for formatters of composite objects (complex numbers, vectors ...).
 *
 */
public class CompositeFormat {

    /**
     * Class contains only static methods.
     */
    private CompositeFormat() {}

    /**
     * Create a default number format.  The default number format is based on
     * {@link NumberFormat#getInstance()} with the only customizing that the
     * maximum number of fraction digits is set to 10.
     * @return the default number format.
     */
    public static NumberFormat getDefaultNumberFormat() {
        return getDefaultNumberFormat(Locale.getDefault());
    }

    /**
     * Create a default number format.  The default number format is based on
     * {@link NumberFormat#getInstance(java.util.Locale)} with the only
     * customizing that the maximum number of fraction digits is set to 10.
     * @param locale the specific locale used by the format.
     * @return the default number format specific to the given locale.
     */
    public static NumberFormat getDefaultNumberFormat(final Locale locale) {
        final NumberFormat nf = NumberFormat.getInstance(locale);
        nf.setMaximumFractionDigits(10);
        return nf;
    }

    /**
     * Parses <code>source until a non-whitespace character is found.
     *
     * @param source the string to parse
     * @param pos input/output parsing parameter.  On output, <code>pos
     *        holds the index of the next non-whitespace character.
     */
    public static void parseAndIgnoreWhitespace(final String source,
                                                final ParsePosition pos) {
        parseNextCharacter(source, pos);
        pos.setIndex(pos.getIndex() - 1);
    }

    /**
     * Parses <code>source until a non-whitespace character is found.
     *
     * @param source the string to parse
     * @param pos input/output parsing parameter.
     * @return the first non-whitespace character.
     */
    public static char parseNextCharacter(final String source,
                                          final ParsePosition pos) {
         int index = pos.getIndex();
         final 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;
    }

    /**
     * Parses <code>source for special double values.  These values
     * include Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY.
     *
     * @param source the string to parse
     * @param value the special value to parse.
     * @param pos input/output parsing parameter.
     * @return the special number.
     */
    private static Number parseNumber(final String source, final double value,
                                      final ParsePosition pos) {
        Number ret = null;

        StringBuilder sb = new StringBuilder();
        sb.append('(');
        sb.append(value);
        sb.append(')');

        final int n = sb.length();
        final int startIndex = pos.getIndex();
        final int endIndex = startIndex + n;
        if (endIndex < source.length() &&
            source.substring(startIndex, endIndex).compareTo(sb.toString()) == 0) {
            ret = Double.valueOf(value);
            pos.setIndex(endIndex);
        }

        return ret;
    }

    /**
     * Parses <code>source for a number.  This method can parse normal,
     * numeric values as well as special values.  These special values include
     * Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY.
     *
     * @param source the string to parse
     * @param format the number format used to parse normal, numeric values.
     * @param pos input/output parsing parameter.
     * @return the parsed number.
     */
    public static Number parseNumber(final String source, final NumberFormat format,
                                     final ParsePosition pos) {
        final int startIndex = pos.getIndex();
        Number number = format.parse(source, pos);
        final int endIndex = pos.getIndex();

        // check for error parsing number
        if (startIndex == endIndex) {
            // try parsing special numbers
            final double[] special = {
                Double.NaN, Double.POSITIVE_INFINITY, Double.NEGATIVE_INFINITY
            };
            for (int i = 0; i < special.length; ++i) {
                number = parseNumber(source, special[i], pos);
                if (number != null) {
                    break;
                }
            }
        }

        return number;
    }

    /**
     * Parse <code>source for an expected fixed string.
     * @param source the string to parse
     * @param expected expected string
     * @param pos input/output parsing parameter.
     * @return true if the expected string was there
     */
    public static boolean parseFixedstring(final String source,
                                           final String expected,
                                           final ParsePosition pos) {

        final int startIndex = pos.getIndex();
        final int endIndex = startIndex + expected.length();
        if ((startIndex >= source.length()) ||
            (endIndex > source.length()) ||
            (source.substring(startIndex, endIndex).compareTo(expected) != 0)) {
            // set index back to start, error index should be the start index
            pos.setIndex(startIndex);
            pos.setErrorIndex(startIndex);
            return false;
        }

        // the string was here
        pos.setIndex(endIndex);
        return true;
    }

    /**
     * Formats a double value to produce a string.  In general, the value is
     * formatted using the formatting rules of <code>format.  There are
     * three exceptions to this:
     * <ol>
     * <li>NaN is formatted as '(NaN)'
     * <li>Positive infinity is formatted as '(Infinity)'
     * <li>Negative infinity is formatted as '(-Infinity)'
     * </ol>
     *
     * @param value the double to format.
     * @param format the format used.
     * @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 static StringBuffer formatDouble(final double value, final NumberFormat format,
                                            final StringBuffer toAppendTo,
                                            final FieldPosition pos) {
        if( Double.isNaN(value) || Double.isInfinite(value) ) {
            toAppendTo.append('(');
            toAppendTo.append(value);
            toAppendTo.append(')');
        } else {
            format.format(value, toAppendTo, pos);
        }
        return toAppendTo;
    }
}

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