How to use

Dimension

in

javax.measure

/**
 * Returns the fundamental dimension for the one specified. If the specified dimension is a dimensional product, the dimensional product of its
 * fundamental dimensions is returned. Physical quantities are considered commensurate only if their fundamental dimensions are equals using the
 * current physics model.
 *
 * @param dimension
 *          the dimension for which the fundamental dimension is returned.
 * @return <code>this</code> or a rational product of fundamental dimension.
 */
public Dimension getFundamentalDimension(Dimension dimension) {
 Map<? extends Dimension, Integer> dimensions = dimension.getBaseDimensions();
 if (dimensions == null)
  return dimension; // Fundamental dimension.
 // Dimensional Product.
 Dimension fundamentalProduct = QuantityDimension.NONE;
 for (Map.Entry<? extends Dimension, Integer> e : dimensions.entrySet()) {
  fundamentalProduct = fundamentalProduct.multiply(this.getFundamentalDimension(e.getKey())).pow(e.getValue());
 }
 return fundamentalProduct;
}

@Override
public Dimension getDimension() {
 Dimension dimension = QuantityDimension.NONE;
 for (int i = 0; i < this.getUnitCount(); i++) {
  Unit<?> unit = this.getUnit(i);
  if (this.elements != null && unit.getDimension() != null) {
   Dimension d = unit.getDimension().pow(this.getUnitPow(i)).root(this.getUnitRoot(i));
   dimension = dimension.multiply(d);
  }
 }
 return dimension;
}

/**
 * Returns the specific detectivity dimension, which is T^2.5 / (M⋅L).
 */
static Dimension specificDetectivity() {
  return TIME.pow(2).divide(MASS.multiply(LENGTH)).multiply(TIME.root(2));
}

/**
 * Returns {@code true} if the given dimension has no components.
 */
static boolean isDimensionless(final Dimension dim) {
  if (dim instanceof UnitDimension) {
    return ((UnitDimension) dim).isDimensionless();
  } else if (dim != null) {
    // Fallback for foreigner implementations.
    final Map<? extends Dimension, Integer> bases = dim.getBaseDimensions();
    if (bases != null) return bases.isEmpty();
  }
  return false;       // Unit is a base unit (not a product of existing units).
}

/**
 * Tests {@link UnitDimension#multiply(Dimension)}.
 */
@Test
@DependsOnMethod("testEqualsAndHashCode")
public void testMultiply() {
  assertSame(LENGTH, LENGTH.multiply(DIMENSIONLESS));
  assertSame(AREA,   LENGTH.multiply(LENGTH));
  assertSame(VOLUME, LENGTH.multiply(AREA));
  assertSame(VOLUME, AREA  .multiply(LENGTH));
  final Map<Dimension,Integer> expected = new HashMap<>(4);
  assertNull(expected.put(LENGTH, 1));
  assertNull(expected.put(TIME,   1));
  assertMapEquals(expected, LENGTH.multiply(TIME).getBaseDimensions());
}

/**
 * Returns the quotient of this dimension with the one specified.
 *
 * @param that
 *          the dimension divisor.
 * @return <code>this.multiply(that.pow(-1))</code>
 * @since 1.0
 */
public Dimension divide(Dimension that) {
 return this.multiply(that.pow(-1));
}

/**
 * Tests {@link UnitDimension#root(int)}.
 */
@Test
@DependsOnMethod("testEqualsAndHashCode")
public void testRoot() {
  assertSame("DIMENSIONLESS", DIMENSIONLESS, DIMENSIONLESS.root(4));
  assertSame("AREA",          LENGTH,        AREA.root(2));
  assertSame("VOLUME",        LENGTH,        VOLUME.root(3));
}

/**
 * Tests {@link UnitDimension#divide(Dimension)}.
 */
@Test
@DependsOnMethod("testEqualsAndHashCode")
public void testDivide() {
  assertSame(LENGTH, LENGTH.divide(DIMENSIONLESS));
  assertSame(LENGTH, AREA  .divide(LENGTH));
  assertSame(LENGTH, VOLUME.divide(AREA));
  assertSame(AREA,   VOLUME.divide(LENGTH));
  assertSame(SPEED,  LENGTH.divide(TIME));
}

/**
 * Returns the base dimensions and their exponents whose product make the given dimension.
 * If the given dimension is a base dimension, then this method returns {@code this} raised
 * to power 1. This method never returns {@code null}.
 */
@SuppressWarnings("ReturnOfCollectionOrArrayField")     // Safe because the map is unmodifiable.
private static Map<? extends Dimension, Fraction> getBaseDimensions(final Dimension dimension) {
  if (dimension instanceof UnitDimension) {
    return ((UnitDimension) dimension).components;
  }
  /*
   * Fallback for non-SIS implementations. The cast from <? extends Dimension> to <Dimension>
   * is safe if we use the 'components' map as a read-only map (no put operation allowed).
   */
  @SuppressWarnings("unchecked")
  Map<Dimension,Integer> components = (Map<Dimension,Integer>) dimension.getBaseDimensions();
  if (components == null) {
    return Collections.singletonMap(dimension, new Fraction(1,1));
  }
  return ObjectConverters.derivedValues(components, Dimension.class, FractionConverter.FromInteger.INSTANCE);
}

/**
 * Returns the quotient of this dimension with the one specified.
 *
 * @param that
 *          the dimension divisor.
 * @return <code>this.multiply(that.pow(-1))</code>
 * @since 1.0
 */
public Dimension divide(Dimension that) {
 return this.multiply(that.pow(-1));
}

/**
 * Returns the fundamental dimension for the one specified. If the specified dimension is a dimensional product, the dimensional product of its
 * fundamental dimensions is returned. Physical quantities are considered commensurate only if their fundamental dimensions are equals using the
 * current physics model.
 *
 * @param dimension
 *          the dimension for which the fundamental dimension is returned.
 * @return <code>this</code> or a rational product of fundamental dimension.
 */
public Dimension getFundamentalDimension(Dimension dimension) {
 Map<? extends Dimension, Integer> dimensions = dimension.getBaseDimensions();
 if (dimensions == null)
  return dimension; // Fundamental dimension.
 // Dimensional Product.
 Dimension fundamentalProduct = QuantityDimension.NONE;
 for (Map.Entry<? extends Dimension, Integer> e : dimensions.entrySet()) {
  fundamentalProduct = fundamentalProduct.multiply(this.getFundamentalDimension(e.getKey())).pow(e.getValue());
 }
 return fundamentalProduct;
}

@Override
public Dimension getDimension() {
 Dimension dimension = QuantityDimension.NONE;
 for (int i = 0; i < this.getUnitCount(); i++) {
  Unit<?> unit = this.getUnit(i);
  if (this.elements != null && unit.getDimension() != null) {
   Dimension d = unit.getDimension().pow(this.getUnitPow(i)).root(this.getUnitRoot(i));
   dimension = dimension.multiply(d);
  }
 }
 return dimension;
}

/**
 * Returns the base dimensions and their exponents whose product make the given dimension.
 * If the given dimension is a base dimension, then this method returns {@code this} raised
 * to power 1. This method never returns {@code null}.
 */
@SuppressWarnings("ReturnOfCollectionOrArrayField")     // Safe because the map is unmodifiable.
private static Map<? extends Dimension, Fraction> getBaseDimensions(final Dimension dimension) {
  if (dimension instanceof UnitDimension) {
    return ((UnitDimension) dimension).components;
  }
  /*
   * Fallback for non-SIS implementations. The cast from <? extends Dimension> to <Dimension>
   * is safe if we use the 'components' map as a read-only map (no put operation allowed).
   */
  @SuppressWarnings("unchecked")
  Map<Dimension,Integer> components = (Map<Dimension,Integer>) dimension.getBaseDimensions();
  if (components == null) {
    return Collections.singletonMap(dimension, new Fraction(1,1));
  }
  return ObjectConverters.derivedValues(components, Dimension.class, FractionConverter.FromInteger.INSTANCE);
}

/**
 * Returns the quotient of this dimension with the one specified.
 *
 * @param that
 *          the dimension divisor.
 * @return <code>this.multiply(that.pow(-1))</code>
 * @since 1.0
 */
public Dimension divide(Dimension that) {
 return this.multiply(that.pow(-1));
}

/**
 * Returns the fundamental dimension for the one specified. If the specified dimension is a dimensional product, the dimensional product of its
 * fundamental dimensions is returned. Physical quantities are considered commensurate only if their fundamental dimensions are equals using the
 * current physics model.
 *
 * @param dimension
 *          the dimension for which the fundamental dimension is returned.
 * @return <code>this</code> or a rational product of fundamental dimension.
 */
public Dimension getFundamentalDimension(Dimension dimension) {
 Map<? extends Dimension, Integer> dimensions = dimension.getBaseDimensions();
 if (dimensions == null)
  return dimension; // Fundamental dimension.
 // Dimensional Product.
 Dimension fundamentalProduct = QuantityDimension.NONE;
 for (Map.Entry<? extends Dimension, Integer> e : dimensions.entrySet()) {
  fundamentalProduct = fundamentalProduct.multiply(this.getFundamentalDimension(e.getKey())).pow(e.getValue());
 }
 return fundamentalProduct;
}

@Override
public Dimension getDimension() {
 Dimension dimension = QuantityDimension.NONE;
 for (int i = 0; i < this.getUnitCount(); i++) {
  Unit<?> unit = this.getUnit(i);
  if (this.elements != null && unit.getDimension() != null) {
   Dimension d = unit.getDimension().pow(this.getUnitPow(i)).root(this.getUnitRoot(i));
   if (dimension != null) {
    dimension = dimension.multiply(d);
   } else {
    dimension = d; // XXX hackaround
   }
  }
 }
 return dimension;
}

Map<? extends Dimension, Integer> dimensions = dimension.getBaseDimensions();
if (dimensions == null)
 return AbstractConverter.IDENTITY; // Fundamental dimension.

/**
 * Tests {@link UnitDimension#pow(int)}.
 */
@Test
@DependsOnMethod("testEqualsAndHashCode")
public void testPow() {
  assertSame("DIMENSIONLESS", DIMENSIONLESS, DIMENSIONLESS.pow(4));
  assertSame("AREA",          AREA,          LENGTH.pow(2));
  assertSame("VOLUME",        VOLUME,        LENGTH.pow(3));
}

Map<? extends Dimension, Integer> dimensions = dimension.getBaseDimensions();
if (dimensions == null)
 return AbstractConverter.IDENTITY; // Fundamental dimension.

Map<? extends Dimension, Integer> dimensions = dimension.getBaseDimensions();
if (dimensions == null)
 return AbstractConverter.IDENTITY; // Fundamental dimension.