ucar.units.BaseUnit Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of udunits Show documentation
The ucar.units Java package is for decoding and encoding formatted unit specifications (e.g. "m/s"), converting numeric values between compatible units (e.g. between "m/s" and "knot"), and for performing arithmetic operations on units (e.g. dividing one unit by another, or raising a unit to a power).
The newest version!
/*
 * Copyright (c) 1998-2018 University Corporation for Atmospheric Research/Unidata
 * See LICENSE for license information.
 */
package ucar.units;

import javax.annotation.concurrent.Immutable;
import java.util.SortedMap;
import java.util.TreeMap;

/**
 * Provides support for base units.
 * 
 * @author Steven R. Emmerson
 */
@Immutable
public class BaseUnit extends DerivedUnitImpl implements Base {
    private static final long                              serialVersionUID = 1L;

    /**
     * The identifier-to-unit map.
     * 
     * @serial
     */
    private static final SortedMap     nameMap          = new TreeMap<>();

    /**
     * The quantity-to-unit map.
     * 
     * @serial
     */
    private static final SortedMap quantityMap      = new TreeMap<>();

    /**
     * The base quantity associated with this base unit.
     * 
     * @serial
     */
    private final BaseQuantity                             baseQuantity;

    /**
     * Constructs from identifiers and a base quantity.
     * 
     * @param id
     *            The identifiers for the base unit. 
     *				id.getSymbol()
     *            shall not return 
     *				null.
     * @param baseQuantity
     *            The base quantity of the base unit.
     * @throws NameException
     *             id.getSymbol() returned 
     *				null.
     */
    protected BaseUnit(final UnitName id, final BaseQuantity baseQuantity)
            throws NameException {
        super(id);
        if (id.getSymbol() == null) {
            throw new NameException("Base unit must have symbol");
        }
        setDimension(new UnitDimension(this));
        this.baseQuantity = baseQuantity;
    }

    /**
     * Factory method for creating a new BaseUnit or obtaining a
     * previously-created one.
     * 
     * @param id
     *            The identifier for the base unit. 
     *				id.getSymbol()
     *            shall not return 
     *				null.
     * @param baseQuantity
     *            The base quantity of the base unit.
     * @throws NameException
     *             id.getSymbol() returned 
     *				null.
     * @throws UnitExistsException
     *             Attempt to incompatibly redefine an existing base unit.
     */
    public static synchronized BaseUnit getOrCreate(final UnitName id,
            final BaseQuantity baseQuantity) throws NameException,
            UnitExistsException {
        BaseUnit baseUnit;
        final BaseUnit nameUnit = nameMap.get(id);
        final BaseUnit quantityUnit = quantityMap.get(baseQuantity);
        if (nameUnit != null || quantityUnit != null) {
            baseUnit = nameUnit != null
                    ? nameUnit
                    : quantityUnit;
            if ((nameUnit != null && !baseQuantity.equals(nameUnit
                    .getBaseQuantity()))
                    || (quantityUnit != null && !id.equals(quantityUnit
                            .getUnitName()))) {
                throw new UnitExistsException(
                        "Attempt to incompatibly redefine base unit \""
                                + baseUnit + '"');
            }
        }
        else {
            baseUnit = new BaseUnit(id, baseQuantity);
            quantityMap.put(baseQuantity, baseUnit);
            nameMap.put(id, baseUnit);
        }
        return baseUnit;
    }

    /**
     * Returns the base quantity associated with this base unit.
     * 
     * @return The base quantity associated with this base unit.
     */
    public final BaseQuantity getBaseQuantity() {
        return baseQuantity;
    }

    /**
     * Returns the identifier for this base unit. This is identical to
     * getSymbol().
     * 
     * @return The identifier for this base unit.
     */
    public final String getID() {
        return getSymbol();
    }

    /**
     * Returns the string representation of this base unit. This is identical to
     * getID().
     * 
     * @return The string representation of this base unit.
     */
    @Override
    public final String toString() {
        return getID();
    }

    /**
     * Indicates if this base unit is dimensionless.
     * 
     * @return true if and only if this base unit is dimensionless
     *         (e.g. "radian").
     */
    @Override
    public boolean isDimensionless() {
        return baseQuantity.isDimensionless();
    }

    /**
     * Tests this class.
     */
    public static void main(final String[] args) throws Exception {
        final BaseUnit meter = new BaseUnit(UnitName.newUnitName("meter", null,
                "m"), BaseQuantity.LENGTH);
        System.out
                .println("meter.getBaseQuantity()=" + meter.getBaseQuantity());
        System.out
                .println("meter.toDerivedUnit(1.)=" + meter.toDerivedUnit(1.));
        System.out.println("meter.toDerivedUnit(new float[] {2})[0]="
                + meter.toDerivedUnit(new float[] { 2 }, new float[1])[0]);
        System.out.println("meter.fromDerivedUnit(1.)="
                + meter.fromDerivedUnit(1.));
        System.out.println("meter.fromDerivedUnit(new float[] {3})[0]="
                + meter.fromDerivedUnit(new float[] { 3 }, new float[1])[0]);
        System.out.println("meter.isCompatible(meter)="
                + meter.isCompatible(meter));
        final BaseUnit radian = new BaseUnit(UnitName.newUnitName("radian",
                null, "rad"), BaseQuantity.PLANE_ANGLE);
        System.out.println("meter.isCompatible(radian)="
                + meter.isCompatible(radian));
        System.out
                .println("meter.isDimensionless()=" + meter.isDimensionless());
        System.out.println("radian.isDimensionless()="
                + radian.isDimensionless());
    }
}