javax.measure.unit
Class Unit<Q extends Quantity>

java.lang.Object
  javax.measure.unit.Unit<Q>

All Implemented Interfaces:

java.io.Serializable

Direct Known Subclasses:

BaseUnit, DerivedUnit

public abstract class Unit<Q extends Quantity>
extends java.lang.Object
implements java.io.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 system 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.

Version:

3.2, August 28, 2006

Author:

Jean-Marie Dautelle, Steve Emmerson, Martin Desruisseaux

See Also:

Wikipedia: Units of measurement, Serialized Form

Field Summary

static Unit<Dimensionless>

ONE Holds the dimensionless unit ONE.

Method Summary

<T extends Quantity> Unit<T>	asType(java.lang.Class<T> type) Casts this unit to a parameterized unit of specified nature.
CompoundUnit<Q>	compound(Unit<Q> subunit) Returns the combination of this unit with the specified sub-unit.
Unit<Q>	divide(double divisor) Returns the result of dividing this unit by an approximate divisor.
Unit<Q>	divide(long divisor) Returns the result of dividing this unit by an exact divisor.
Unit<? extends Quantity>	divide(Unit that) Returns the quotient of this unit with the one specified.
abstract boolean	equals(java.lang.Object that) Indicates if the specified unit can be considered equals to the one specified.
UnitConverter	getConverterTo(Unit that) Returns a converter of numeric values from this unit to another unit.
Dimension	getDimension() Returns the dimension of this unit (depends upon the current dimensional model).
abstract Unit<? super Q>	getSystemUnit() 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.
Unit<? extends Quantity>	inverse() Returns the inverse of this unit.
boolean	isCompatible(Unit that) Indicates if this unit is compatible with the unit specified.
Unit<Q>	plus(double offset) Returns the result of adding an offset to this unit.
Unit<? extends Quantity>	pow(int n) Returns a unit equals to this unit raised to an exponent.
Unit<? extends Quantity>	root(int n) Returns a unit equals to the given root of this unit.
Unit<Q>	times(double factor) Returns the result of multiplying this unit by a an approximate factor
Unit<Q>	times(long factor) Returns the result of multiplying this unit by an exact factor.
Unit<? extends Quantity>	times(Unit that) Returns the product of this unit with the one specified.
java.lang.String	toString() Returns the standard String representation of this unit.
abstract UnitConverter	toSystemUnit() Returns the converter from this unit to its system unit.
Unit<Q>	transform(UnitConverter operation) Returns the unit derived from this unit using the specified converter.
static Unit<? extends Quantity>	valueOf(java.lang.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 Detail

ONE

public static final Unit<Dimensionless> ONE

Holds the dimensionless unit ONE.

Method Detail

getSystemUnit

public abstract Unit<? super Q> getSystemUnit()

Returns the base unit, alternate unit or product of base units and alternate units this unit is derived from. The system unit identifies the "type" of quantity for which this unit is employed. For example:

    boolean isAngularVelocity(Unit<?> u) {
       return u.getSystemUnit().equals(RADIAN.divide(SECOND));
    }
    assert(REVOLUTION.divide(MINUTE).isAngularVelocity());  
 

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.

toSystemUnit

public abstract UnitConverter toSystemUnit()

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 java.lang.Object

Returns:

this unit hashcode value.

equals

public abstract boolean equals(java.lang.Object that)

Indicates if the specified unit can be considered equals to the one specified.

Overrides:

equals in class java.lang.Object

Parameters:

that - the object to compare to.

Returns:

true if this unit is considered equal to that unit; false otherwise.

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:

     RADIAN.equals(ONE) == false
     RADIAN.isCompatible(ONE) == true
 

Parameters:

that - the other unit.

Returns:

this.getDimension().equals(that.getDimension())

See Also:

getDimension()

asType

public final <T extends Quantity> Unit<T> asType(java.lang.Class<T> type)

Casts this unit to a parameterized unit of specified nature. For example:

 Unit<Length> LIGHT_YEAR = NonSI.C.times(NonSI.YEAR).asType(Length.class);
 

Parameters:

type - the quantity class identifying the nature of the unit.

Returns:

this unit parameterized with the specified type.

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)).

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:

   HOUR_MINUTE = NonSI.HOUR.compound(NonSI.MINUTE);
   DEGREE_MINUTE_SECOND_ANGLE = NonSI.DEGREE_ANGLE.compound(
       NonSI.DEGREE_MINUTE).compound(NonSI.SECOND_ANGLE);
  

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:

 Unit<Dimensionless> DECIBEL = Unit.ONE.transform(
     new LogConverter(10).inverse().concatenate(
           new RationalConverter(1, 10)));

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:

java.lang.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(java.lang.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:

java.lang.IllegalArgumentException - if the specified character sequence cannot be correctly parsed (e.g. symbol unknown).

toString

public final java.lang.String toString()

Returns the standard String representation of this unit.

Overrides:

toString in class java.lang.Object

Returns:

UnitFormat.getStandardInstance().format(this)