Package javax.measure.unit

Class Unit<Q extends Quantity>

java.lang.Object
javax.measure.unit.Unit<Q>
All Implemented Interfaces:
Serializable
Direct Known Subclasses:
BaseUnit, DerivedUnit
public abstract class Unit<Q extends Quantity> extends Object implements Serializable

This class represents a determinate quantity (as of length, time, heat, or value) adopted as a standard of measurement.

It is helpful to think of instances of this class as recording the history by which they are created. Thus, for example, the string "g/kg" (which is a dimensionless unit) would result from invoking the method toString() on a unit that was created by dividing a gram unit by a kilogram unit. Yet, "kg" divided by "kg" returns ONE and not "kg/kg" due to automatic unit factorization.

This class supports the multiplication of offsets units. The result is usually a unit not convertible to its standard unit. Such units may appear in derivative quantities. For example °C/m is an unit of gradient, which is common in atmospheric and oceanographic research.

Units raised at rational powers are also supported. For example the cubic root of "liter" is a unit compatible with meter.

Instances of this class are immutable.

See Also:

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final Unit<Dimensionless>
    ONE
    Holds the dimensionless unit ONE.

  • Constructor Summary

    Constructors
    Modifier
    Constructor
    Description
    protected
    Unit()
    Default constructor.

  • Method Summary

    Modifier and Type
    Method
    Description
    final <A extends Quantity>
    AlternateUnit<A>
    alternate(String symbol)
    Returns a unit equivalent to this unit but used in expressions to distinguish between quantities of a different nature but of the same dimensions.
    final <T extends Quantity>
    Unit<T>
    asType(Class<T> type)
    Casts this unit to a parameterized unit of specified nature or throw a ClassCastException if the dimension of the specified quantity and this unit's dimension do not match.
    final CompoundUnit<Q>
    compound(Unit<Q> subunit)
    Returns the combination of this unit with the specified sub-unit.
    final Unit<Q>
    divide(double divisor)
    Returns the result of dividing this unit by an approximate divisor.
    final Unit<Q>
    divide(long divisor)
    Returns the result of dividing this unit by an exact divisor.
    final Unit<? extends Quantity>
    divide(Unit<?> that)
    Returns the quotient of this unit with the one specified.
    abstract boolean
    equals(Object that)
    Indicates if the specified unit can be considered equals to the one specified.
    final UnitConverter
    getConverterTo(Unit<?> that)
    Returns a converter of numeric values from this unit to another unit.
    final Dimension
    getDimension()
    Returns the dimension of this unit (depends upon the current dimensional model).
    abstract Unit<? super Q>
    getStandardUnit()
    Returns the base unit, alternate unit or product of base units and alternate units this unit is derived from.
    abstract int
    hashCode()
    Returns the hash code for this unit.
    final Unit<? extends Quantity>
    inverse()
    Returns the inverse of this unit.
    final boolean
    isCompatible(Unit<?> that)
    Indicates if this unit is compatible with the unit specified.
    boolean
    isStandardUnit()
    Indicates if this unit is a standard unit (base units and alternate units are standard units).
    final Unit<Q>
    plus(double offset)
    Returns the result of adding an offset to this unit.
    final Unit<? extends Quantity>
    pow(int n)
    Returns a unit equals to this unit raised to an exponent.
    final Unit<? extends Quantity>
    root(int n)
    Returns a unit equals to the given root of this unit.
    final Unit<Q>
    times(double factor)
    Returns the result of multiplying this unit by a an approximate factor
    final Unit<Q>
    times(long factor)
    Returns the result of multiplying this unit by an exact factor.
    final Unit<? extends Quantity>
    times(Unit<?> that)
    Returns the product of this unit with the one specified.
    abstract UnitConverter
    toStandardUnit()
    Returns the converter from this unit to its system unit.
    final String
    toString()
    Returns the standard String representation of this unit.
    final Unit<Q>
    transform(UnitConverter operation)
    Returns the unit derived from this unit using the specified converter.
    static Unit<? extends Quantity>
    valueOf(CharSequence csq)
    Returns a unit instance that is defined from the specified character sequence using the standard unit format.

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Field Details

    • ONE

      public static final Unit<Dimensionless> ONE
      Holds the dimensionless unit ONE.

  • Constructor Details

    • Unit

      protected Unit()
      Default constructor.

  • Method Details

    • getStandardUnit

      public abstract Unit<? super Q> getStandardUnit()
      Returns the base unit, alternate unit or product of base units and alternate units this unit is derived from. The standard unit identifies the "type" of quantity for which this unit is employed. For example:[code] boolean isAngularVelocity(Unit<?> u) { return u.getStandardUnit().equals(RADIAN.divide(SECOND)); } assert(REVOLUTION.divide(MINUTE).isAngularVelocity()); [/code]

      Note: Having the same system unit is not sufficient to ensure that a converter exists between the two units (e.g. °C/m and K/m).

      Returns:
      the system unit this unit is derived from.

    • toStandardUnit

      public abstract UnitConverter toStandardUnit()
      Returns the converter from this unit to its system unit.
      Returns:
      this.getConverterTo(this.getSystemUnit())

    • hashCode

      public abstract int hashCode()
      Returns the hash code for this unit.
      Overrides:
      hashCode in class Object
      Returns:
      this unit hashcode value.

    • equals

      public abstract boolean equals(Object that)
      Indicates if the specified unit can be considered equals to the one specified.
      Overrides:
      equals in class Object
      Parameters:
      that - the object to compare to.
      Returns:
      true if this unit is considered equal to that unit; false otherwise.

    • isStandardUnit

      public boolean isStandardUnit()
      Indicates if this unit is a standard unit (base units and alternate units are standard units). The standard unit identifies the "type" of quantity for which the unit is employed.
      Returns:
      getStandardUnit().equals(this)

    • isCompatible

      public final boolean isCompatible(Unit<?> that)
      Indicates if this unit is compatible with the unit specified. Units don't need to be equals to be compatible. For example:[code] RADIAN.equals(ONE) == false RADIAN.isCompatible(ONE) == true [/code]
      Parameters:
      that - the other unit.
      Returns:
      this.getDimension().equals(that.getDimension())
      See Also:

    • asType

      public final <T extends Quantity> Unit<T> asType(Class<T> type) throws ClassCastException
      Casts this unit to a parameterized unit of specified nature or throw a ClassCastException if the dimension of the specified quantity and this unit's dimension do not match. For example:[code] Unit LIGHT_YEAR = NonSI.C.times(NonSI.YEAR).asType(Length.class); [/code]
      Parameters:
      type - the quantity class identifying the nature of the unit.
      Returns:
      this unit parameterized with the specified type.
      Throws:
      ClassCastException - if the dimension of this unit is different from the specified quantity dimension.
      UnsupportedOperationException - if the specified quantity class does not have a public static field named "UNIT" holding the standard unit for the quantity.

    • getDimension

      public final Dimension getDimension()
      Returns the dimension of this unit (depends upon the current dimensional model).
      Returns:
      the dimension of this unit for the current model.

    • getConverterTo

      public final UnitConverter getConverterTo(Unit<?> that) throws ConversionException
      Returns a converter of numeric values from this unit to another unit.
      Parameters:
      that - the unit to which to convert the numeric values.
      Returns:
      the converter from this unit to that unit.
      Throws:
      ConversionException - if the conveter cannot be constructed (e.g. !this.isCompatible(that)).

    • alternate

      public final <A extends Quantity> AlternateUnit<A> alternate(String symbol)
      Returns a unit equivalent to this unit but used in expressions to distinguish between quantities of a different nature but of the same dimensions.

      Examples of alternate units:[code] Unit RADIAN = ONE.alternate("rad"); Unit NEWTON = METER.times(KILOGRAM).divide(SECOND.pow(2)).alternate("N"); Unit PASCAL = NEWTON.divide(METER.pow(2)).alternate("Pa"); [/code]

      Parameters:
      symbol - the new symbol for the alternate unit.
      Returns:
      the alternate unit.
      Throws:
      UnsupportedOperationException - if this unit is not a standard unit.
      IllegalArgumentException - if the specified symbol is already associated to a different unit.

    • compound

      public final CompoundUnit<Q> compound(Unit<Q> subunit)
      Returns the combination of this unit with the specified sub-unit. Compound units are typically used for formatting purpose. Examples of compound units:[code] HOUR_MINUTE = NonSI.HOUR.compound(NonSI.MINUTE); DEGREE_MINUTE_SECOND_ANGLE = NonSI.DEGREE_ANGLE.compound( NonSI.DEGREE_MINUTE).compound(NonSI.SECOND_ANGLE); [/code]
      Parameters:
      subunit - the sub-unit to combine with this unit.
      Returns:
      the corresponding compound unit.

    • transform

      public final Unit<Q> transform(UnitConverter operation)
      Returns the unit derived from this unit using the specified converter. The converter does not need to be linear. For example:[code] Unit DECIBEL = Unit.ONE.transform( new LogConverter(10).inverse().concatenate( new RationalConverter(1, 10)));[/code]
      Parameters:
      operation - the converter from the transformed unit to this unit.
      Returns:
      the unit after the specified transformation.

    • plus

      public final Unit<Q> plus(double offset)
      Returns the result of adding an offset to this unit. The returned unit is convertible with all units that are convertible with this unit.
      Parameters:
      offset - the offset added (expressed in this unit, e.g. CELSIUS = KELVIN.plus(273.15)).
      Returns:
      this.transform(new AddConverter(offset))

    • times

      public final Unit<Q> times(long factor)
      Returns the result of multiplying this unit by an exact factor.
      Parameters:
      factor - the exact scale factor (e.g. KILOMETER = METER.times(1000)).
      Returns:
      this.transform(new RationalConverter(factor, 1))

    • times

      public final Unit<Q> times(double factor)
      Returns the result of multiplying this unit by a an approximate factor
      Parameters:
      factor - the approximate factor (e.g. ELECTRON_MASS = KILOGRAM.times(9.10938188e-31)).
      Returns:
      this.transform(new MultiplyConverter(factor))

    • times

      public final Unit<? extends Quantity> times(Unit<?> that)
      Returns the product of this unit with the one specified.
      Parameters:
      that - the unit multiplicand.
      Returns:
      this * that

    • inverse

      public final Unit<? extends Quantity> inverse()
      Returns the inverse of this unit.
      Returns:
      1 / this

    • divide

      public final Unit<Q> divide(long divisor)
      Returns the result of dividing this unit by an exact divisor.
      Parameters:
      divisor - the exact divisor. (e.g. QUART = GALLON_LIQUID_US.divide(4)).
      Returns:
      this.transform(new RationalConverter(1 , divisor))

    • divide

      public final Unit<Q> divide(double divisor)
      Returns the result of dividing this unit by an approximate divisor.
      Parameters:
      divisor - the approximate divisor.
      Returns:
      this.transform(new MultiplyConverter(1.0 / divisor))

    • divide

      public final Unit<? extends Quantity> divide(Unit<?> that)
      Returns the quotient of this unit with the one specified.
      Parameters:
      that - the unit divisor.
      Returns:
      this / that

    • root

      public final Unit<? extends Quantity> root(int n)
      Returns a unit equals to the given root of this unit.
      Parameters:
      n - the root's order.
      Returns:
      the result of taking the given root of this unit.
      Throws:
      ArithmeticException - if n == 0.

    • pow

      public final Unit<? extends Quantity> pow(int n)
      Returns a unit equals to this unit raised to an exponent.
      Parameters:
      n - the exponent.
      Returns:
      the result of raising this unit to the exponent.

    • valueOf

      public static Unit<? extends Quantity> valueOf(CharSequence csq)
      Returns a unit instance that is defined from the specified character sequence using the standard unit format.

      Examples of valid entries (all for meters per second squared) are:

      • m*s-2
      • m/s²
      • m·s-²
      • m*s**-2
      • m^+1 s^-2

      Parameters:
      csq - the character sequence to parse.
      Returns:
      UnitFormat.getStandardInstance().parse(csq, new ParsePosition(0))
      Throws:
      IllegalArgumentException - if the specified character sequence cannot be correctly parsed (e.g. symbol unknown).

    • toString

      public final String toString()
      Returns the standard String representation of this unit. This representation is not affected by locale. Locale-sensitive unit formatting and parsing is handled by the MeasureFormat class and its subclasses.
      Overrides:
      toString in class Object
      Returns:
      UnitFormat.getStandardInstance().format(this)