NumberUtil.java

/*
 * RHQ Management Platform
 * Copyright (C) 2005-2008 Red Hat, Inc.
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation, and/or the GNU Lesser
 * General Public License, version 2.1, also as published by the Free
 * Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 * GNU General Public License and the GNU Lesser General Public License
 * for more details.
 *
 * You should have received a copy of the GNU General Public License
 * and the GNU Lesser General Public License along with this program;
 * if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 */
package org.rhq.core.util;

import java.text.NumberFormat;
import java.text.ParseException;

/**
 * Utilities for dealing with number parsing / formatting. This class is mainly meant to be used by java beans and other
 * classes that must do number formatting but cannot throw any exceptions during the process.
 */

public final class NumberUtil {
    /**
     * Constant value representing "not a number".
     */
    public static final Number NaN = Double.NaN;

    // static class, privatize ctor
    private NumberUtil() {
    }

    /**
     * Parse the <code>input</code> string (using the default locale) and return its numeric representation. If the
     * <code>input</code> string is null, empty or cannot be parsed, return <code>{@link Double#NaN} <code>.
     */
    public static Number stringAsNumber(String input) {
        return _parse(input, NumberFormat.getNumberInstance());
    }

    /**
     * Format the <code>input</code> number as a string (using the default locale). If the <code>input</code> number is
     * <code>{@link Double#NaN}</code>, return null.
     */
    public static String numberAsString(double input) {
        return _format(input, NumberFormat.getNumberInstance());
    }

    /**
     * Parse the <code>input</code> string (using the default locale) and return its numeric percentage representation.
     * If the <code>input</code> string is null, empty or cannot be parsed, return <code>{@link Double#NaN} <code>.
     */
    public static Number stringAsPercentage(String input) {
        return _parse(input, NumberFormat.getPercentInstance());
    }

    /**
     * Format the <code>input</code> percentage as a string (using the default locale). If the <code>input</code>
     * percentage is <code>{@link Double#NaN}</code>, return null.
     */
    public static String percentageAsString(double input) {
        return _format(input, NumberFormat.getPercentInstance());
    }

    /**
     * Given an old version string, this attempts to auto-generate a new incremented version.
     * 
     * @param oldVersion the version to increment
     * @return the auto-incremented version
     */
    public static String autoIncrementVersion(String oldVersion) {
        String newVersion = "1.0";
        if (oldVersion != null && oldVersion.length() != 0) {
            String[] parts = oldVersion.split("[^a-zA-Z0-9]");
            String lastPart = parts[parts.length - 1];
            try {
                int lastNumber = Integer.parseInt(lastPart);
                newVersion = oldVersion.substring(0, oldVersion.length() - lastPart.length()) + (lastNumber + 1);
            } catch (NumberFormatException nfe) {
                newVersion = oldVersion + ".1";
            }
        }
        return newVersion;
    }

    //------------------------------------------------------------------
    //-- private helpers
    //------------------------------------------------------------------
    private static Number _parse(String input, NumberFormat fmt) {
        if ((null != input) && (input.trim().length() > 0)) {
            try {
                return fmt.parse(input);
            } catch (ParseException e) {
                return NaN;
            }
        } else {
            return NaN;
        }
    }

    private static String _format(double input, NumberFormat fmt) {
        if (NaN.doubleValue() != input) {
            return fmt.format(input);
        } else {
            return null;
        }
    }
}

// EOF