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Unit Standard (JSR 363) Reference Implementation.
There is a newer version: 1.0.3
/*
 *  Unit-API - Units of Measurement API for Java
 *  Copyright (c) 2005-2015, Jean-Marie Dautelle, Werner Keil, V2COM.
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 *
 * 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
 *
 * 3. Neither the name of JSR-363 nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
package tec.units.ri.format;

import java.io.IOException;
import java.text.FieldPosition;

import javax.measure.Unit;
import javax.measure.format.ParserException;
import javax.measure.format.UnitFormat;

import tec.units.ri.AbstractUnit;

/**
 * 
 * This class provides the interface for formatting and parsing
 * {@link AbstractUnit units}.
 * 
 *
 * 
 * For all metric units, the 20 SI prefixes used to form decimal multiples and
 * sub-multiples of SI units are recognized. {@link USCustomary US Customary}
 * units are directly recognized. For example:[code]
 * Unit.valueOf("m°C").equals(SI.MILLI(SI.CELSIUS))
 * Unit.valueOf("kW").equals(SI.KILO(SI.WATT))
 * Unit.valueOf("ft").equals(SI.METRE.multiply(3048).divide(10000))[/code]
 * 
 *
 * @author Jean-Marie Dautelle
 * @author Werner Keil
 * @version 0.7 $Date: 2015-07-05 $
 * 
 */
public abstract class AbstractUnitFormat implements UnitFormat {

	/**
	 * Returns the {@link SymbolMap} for this unit format.
	 *
	 * @return the symbol map used by this format.
	 */
	protected abstract SymbolMap getSymbols();

	/**
	 * Formats an object to produce a string. This is equivalent to 
	 * {@link #format(Object, StringBuffer, FieldPosition) format}(obj,
	 *         new StringBuffer(), new FieldPosition(0)).toString();
	 * 
	 *
	 * @param obj
	 *            The object to format
	 * @return Formatted string.
	 * @exception IllegalArgumentException
	 *                if the Format cannot format the given object
	 */
	public final String format(Unit unit) {
		if (unit instanceof AbstractUnit) {
			return format((AbstractUnit) unit, new StringBuilder())
					.toString();
		} else {
			try {
				return (this.format(unit, new StringBuilder()))
						.toString();
			} catch (IOException ex) {
				throw new ParserException(ex); // Should never happen.
			}
		}
	}

	/**
	 * Formats the specified unit.
	 *
	 * @param unit
	 *            the unit to format.
	 * @param appendable
	 *            the appendable destination.
	 * @return The appendable destination passed in as {@code appendable}, with
	 *         formatted text appended.
	 * @throws IOException
	 *             if an error occurs.
	 */
	public abstract Appendable format(Unit unit, Appendable appendable)
			throws IOException;

	/**
	 * Parses a portion of the specified CharSequence from the
	 * specified position to produce a unit. If there is no unit to parse
	 * {@link AbstractUnit#ONE} is returned.
	 *
	 * @param csq
	 *            the CharSequence to parse.
	 * @param index
	 *            the current parsing index.
	 * @return the unit parsed from the specified character sub-sequence.
	 * @throws IllegalArgumentException
	 *             if any problem occurs while parsing the specified character
	 *             sequence (e.g. illegal syntax).
	 */
	protected abstract Unit parse(CharSequence csq, int index)
			throws IllegalArgumentException;

	/**
	 * Convenience method equivalent to
	 * {@link #format(AbstractUnit, Appendable)} except it does not raise an
	 * IOException.
	 *
	 * @param unit
	 *            the unit to format.
	 * @param dest
	 *            the appendable destination.
	 * @return the specified StringBuilder.
	 */
	final StringBuilder format(AbstractUnit unit, StringBuilder dest) {
		try {
			return (StringBuilder) this.format(unit, (Appendable) dest);
		} catch (IOException ex) {
			throw new ParserException(ex); // Should never happen.
		}
	}

	/**
	 * serialVersionUID
	 */
	// private static final long serialVersionUID = -2046025267890654321L;
}