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JPX - Java GPX (GPS) Library
There is a newer version: 3.2.1
/*
 * Java GPX Library (jpx-2.1.0).
 * Copyright (c) 2016-2020 Franz Wilhelmstötter
 *
 * Licensed 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.
 *
 * Author:
 *    Franz Wilhelmstötter ([email protected])
 */
package io.jenetics.jpx;

import static java.lang.String.format;
import static java.util.Objects.requireNonNull;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.Serializable;

/**
 * Extent of something along its greatest dimension or the extent of space
 * between two objects or places. The metric system unit for this quantity is
 * "m" (metre).
 *
 * @author Franz Wilhelmstötter
 * @version 1.2
 * @since 1.0
 */
public final class Length
	extends Number
	implements
		Comparable,
		Serializable
{

	private static final long serialVersionUID = 2L;

	/**
	 * Represents a given length unit.
	 */
	public enum Unit {

		/**
		 * Represents a meter.
		 */
		METER(1.0),

		/**
		 * Represents a kilometer: ≙ 1,000 m.
		 */
		KILOMETER(1_000.0),

		/**
		 * Represents an inch: ≙ 0.0254 m.
		 */
		INCH(127.0/5_000.0),

		/**
		 * Represents a foot: ≙ 0.3048 m.
		 */
		FOOT(0.3048),

		/**
		 * Represents a yard: ≙ 0.9144 m.
		 */
		YARD(1_143.0/1_250.0),

		/**
		 * Represents a statute mile: ≙ 1,609.344 m.
		 */
		MILE(201_168.0/125.0),

		/**
		 * Represents a fathom: ≙ 1.853184 m.
		 */
		FATHOM(1.853184),

		/**
		 * Represents a cable: ≙ 185.3184 m.
		 */
		CABLE(185.3184),

		/**
		 * Represents a nautical mile: ≙ 1,853.184 m.
		 */
		NAUTICAL_MILE(1_853.184);

		private final double _factor;

		Unit(final double factor) {
			_factor = factor;
		}

		/**
		 * Convert the given length value of the given {@code sourceUnit} into a
		 * length value of {@code this} length unit. The given example converts 3
		 * inches into yards.
		 *
		 * {@code
		 * final double yards = YARD.convert(3, INCH);
		 * }
		 *
		 * @param length the length value
		 * @param sourceUnit the source length unit
		 * @return the speed value of {@code this} length unit
		 */
		public double convert(final double length, final Unit sourceUnit) {
			requireNonNull(sourceUnit);
			final double meters = length*sourceUnit._factor;
			return meters/_factor;
		}
	}

	private final double _value;

	/**
	 * Create a new {@code Length} object with the given value in meters.
	 *
	 * @param value the value (in meters) of the new {@code Length} object
	 */
	private Length(final double value) {
		_value = value;
	}

	/**
	 * Return the length in meter.
	 *
	 * @return the length in meter
	 */
	@Override
	public double doubleValue() {
		return _value;
	}

	/**
	 * Return the length in the desired unit.
	 *
	 * @param unit the desired length unit
	 * @return the length in the desired unit
	 * @throws NullPointerException if the given length {@code unit} is
	 *         {@code null}
	 */
	public double to(final Unit unit) {
		return unit.convert(_value, Unit.METER);
	}

	@Override
	public int intValue() {
		return (int)doubleValue();
	}

	@Override
	public long longValue() {
		return (long)doubleValue();
	}

	@Override
	public float floatValue() {
		return (float)doubleValue();
	}

	@Override
	public int compareTo(final Length other) {
		return Double.compare(_value, other._value);
	}

	@Override
	public int hashCode() {
		return Double.hashCode(_value);
	}

	@Override
	public boolean equals(final Object obj) {
		return obj == this ||
			obj instanceof Length &&
			Double.compare(((Length)obj)._value, _value) == 0;
	}

	@Override
	public String toString() {
		return format("%s m", _value);
	}


	/* *************************************************************************
	 *  Static object creation methods
	 * ************************************************************************/

	/**
	 * Create a new {@code Length} object with the given length.
	 *
	 * @param length the length
	 * @param unit the length unit
	 * @return a new {@code Length} object with the given length.
	 * @throws NullPointerException if the given length {@code unit} is
	 *         {@code null}
	 */
	public static Length of(final double length, final Unit unit) {
		requireNonNull(unit);
		return new Length(Unit.METER.convert(length, unit));
	}

	static Length parse(final String value) {
		final String length = Strings.trim(value);

		return length != null
			? Length.of(Double.parseDouble(length), Unit.METER)
			: null;
	}

	/* *************************************************************************
	 *  Java object serialization
	 * ************************************************************************/

	private Object writeReplace() {
		return new Serial(Serial.LENGTH, this);
	}

	private void readObject(final ObjectInputStream stream)
		throws InvalidObjectException
	{
		throw new InvalidObjectException("Serialization proxy required.");
	}

	void write(final DataOutput out) throws IOException {
		out.writeDouble(_value);
	}

	static Length read(final DataInput in) throws IOException {
		return new Length(in.readDouble());
	}

}