org.jscience.measure
Class Amount<Q extends Quantity>

java.lang.Object
  extended by org.jscience.measure.Amount<Q>
All Implemented Interfaces:
java.io.Serializable, java.lang.Comparable<Measurable<Q>>, Measurable<Q>, javolution.lang.Immutable

public final class Amount<Q extends Quantity>
extends java.lang.Object
implements Measurable<Q>, java.io.Serializable, javolution.lang.Immutable

This class represents a determinate or estimated amount for which operations such as addition, subtraction, multiplication and division can be performed (it implements the Field interface).

The nature of an amount can be deduced from its parameterization (compile time) or its unit (run time). Its precision is given by its error.

Amounts can be exact, in which case they can be expressed as an exact long integer in the amount unit. The framework tries to keep amount exact as much as possible. For example:[code] Amount m = Amount.valueOf(33, FOOT).divide(11).times(2); System.out.println(m); System.out.println(m.isExact() ? "exact" : "inexact"); System.out.println(m.getExactValue()); > 6 ft > exact > 6[/code]

Errors (including numeric errors) are calculated using numeric intervals. It is possible to resolve systems of linear equations involving matrices, even if the system is close to singularity; in which case the error associated with some (or all) components of the solution may be large.

By default, non-exact amounts are shown using the plus/minus character ('±') (see AmountFormat). For example, "(2.0 ± 0.001) km/s" represents a velocity of 2 km/s with an absolute error of ± 1 m/s. Exact amount use an integer notation (no decimal point, e.g. "2000 m").

Operations between different amounts may or may not be authorized based upon the current PhysicalModel. For example, adding Amount<Length> and Amount<Duration> is not allowed by the StandardModel, but is authorized with the RelativisticModel.

See Also:
Wikipedia: Measuring, Serialized Form

Field Summary
static Amount<Dimensionless> ONE
          Holds a dimensionless measure of one (exact).
protected static javolution.xml.XMLFormat<Amount> XML
          Holds the default XML representation for measures.
static Amount<Dimensionless> ZERO
          Holds a dimensionless measure of zero (exact).
 
Method Summary
 Amount<Q> abs()
          Returns the absolute value of this measure.
 boolean approximates(Amount that)
          Indicates if this measure approximates that measure.
 int compareTo(Measurable<Q> that)
          Compares this measure with the specified measurable object.
 Amount<Q> copy()
           
 Amount<? extends Quantity> divide(Amount that)
          Returns this measure divided by the one specified.
 Amount<Q> divide(double divisor)
          Returns this measure divided by the specified approximate divisor (dimensionless).
 Amount<Q> divide(long divisor)
          Returns this measure divided by the specified exact divisor (dimensionless).
 double doubleValue(Unit<Q> unit)
          Returns the value of this measurable stated in the specified unit as a double.
 boolean equals(java.lang.Object that)
          Compares this measure against the specified object for strict equality (same value interval and same units).
 double getAbsoluteError()
          Returns the value by which theestimated value may differ from the true value (all stated in base units).
 double getEstimatedValue()
          Returns the estimated value for this measure stated in this measure unit.
 long getExactValue()
          Returns the exact value for this measure stated in this measure unit.
 double getMaximumValue()
          Returns the upper bound interval value for this measure stated in this measure unit.
 double getMinimumValue()
          Returns the lower bound interval value for this measure stated in this measure unit.
 double getRelativeError()
          Returns the percentage by which the estimated amount may differ from the true amount.
 Unit<Q> getUnit()
          Returns the unit in which the estimated value and absolute error are stated.
 int hashCode()
          Returns the hash code for this measure.
 Amount<? extends Quantity> inverse()
          Returns the multiplicative inverse of this measure.
 boolean isExact()
          Indicates if this measure amount is exact.
 boolean isGreaterThan(Amount<Q> that)
          Indicates if this measure is ordered after that measure (independently of the measure unit).
 boolean isLargerThan(Amount<Q> that)
          Compares this measure with that measure ignoring the sign.
 boolean isLessThan(Amount<Q> that)
          Indicates if this measure is ordered before that measure (independently of the measure unit).
 long longValue(Unit<Q> unit)
          Returns the estimated integral value of this measurable stated in the specified unit as a long.
 Amount<Q> minus(Amount that)
          Returns the difference of this measure with the one specified.
 Amount<Q> opposite()
          Returns the opposite of this measure.
 Amount<Q> plus(Amount that)
          Returns the sum of this measure with the one specified.
 Amount<? extends Quantity> pow(int exp)
          Returns this measure raised at the specified exponent.
static
<Q extends Quantity>
Amount<Q>
rangeOf(double minimum, double maximum, Unit<Q> unit)
          Returns the measure corresponding to the specified interval stated in the specified unit.
 Amount<? extends Quantity> root(int n)
          Returns the given root of this measure.
 Amount<? extends Quantity> sqrt()
          Returns the square root of this measure.
 Amount<? extends Quantity> times(Amount that)
          Returns the product of this measure with the one specified.
 Amount<Q> times(double factor)
          Returns this measure scaled by the specified approximate factor (dimensionless).
 Amount<Q> times(long factor)
          Returns this measure scaled by the specified exact factor (dimensionless).
<R extends Quantity>
Amount<R>
to(Unit<R> unit)
          Returns the measure equivalent to this measure but stated in the specified unit.
 java.lang.String toString()
          Returns the text representation of this amount as a java.lang.String.
 javolution.text.Text toText()
          Returns the text representation of this measure.
static Amount<?> valueOf(java.lang.CharSequence csq)
          Returns the measure represented by the specified character sequence.
static
<Q extends Quantity>
Amount<Q>
valueOf(double value, double error, Unit<Q> unit)
          Returns the measure corresponding to the specified approximate value and measurement error, both stated in the specified unit.
static
<Q extends Quantity>
Amount<Q>
valueOf(double value, Unit<Q> unit)
          Returns the measure corresponding to an approximate value (double) stated in the specified unit; the precision of the measure is assumed to be the double precision (64 bits IEEE 754 format).
static
<Q extends Quantity>
Amount<Q>
valueOf(long value, Unit<Q> unit)
          Returns the exact measure corresponding to the value stated in the specified unit.
 
Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait
 

Field Detail

ZERO

public static final Amount<Dimensionless> ZERO
Holds a dimensionless measure of zero (exact).


ONE

public static final Amount<Dimensionless> ONE
Holds a dimensionless measure of one (exact).


XML

protected static final javolution.xml.XMLFormat<Amount> XML
Holds the default XML representation for measures. This representation consists of a value, an unit and an optional error attribute when the measure is not exact. The unit attribute determinates the measurement type. For example:
 <Amount value="12" unit="µA"/>
represents an electric current measurement.

Method Detail

valueOf

public static <Q extends Quantity> Amount<Q> valueOf(long value,
                                                     Unit<Q> unit)
Returns the exact measure corresponding to the value stated in the specified unit.

Parameters:
value - the exact value stated in the specified unit.
unit - the unit in which the value is stated.
Returns:
the corresponding measure object.

valueOf

public static <Q extends Quantity> Amount<Q> valueOf(double value,
                                                     Unit<Q> unit)
Returns the measure corresponding to an approximate value (double) stated in the specified unit; the precision of the measure is assumed to be the double precision (64 bits IEEE 754 format).

Parameters:
value - the estimated value (± LSB) stated in the specified unit.
unit - the unit in which the value is stated.
Returns:
the corresponding measure object.

valueOf

public static <Q extends Quantity> Amount<Q> valueOf(double value,
                                                     double error,
                                                     Unit<Q> unit)
Returns the measure corresponding to the specified approximate value and measurement error, both stated in the specified unit.

Parameters:
value - the estimated amount (± error) stated in the specified unit.
error - the measurement error (absolute).
unit - the unit in which the amount and the error are stated.
Returns:
the corresponding measure object.
Throws:
java.lang.IllegalArgumentException - if error < 0.0

rangeOf

public static <Q extends Quantity> Amount<Q> rangeOf(double minimum,
                                                     double maximum,
                                                     Unit<Q> unit)
Returns the measure corresponding to the specified interval stated in the specified unit.

Parameters:
minimum - the lower bound for the measure value.
maximum - the upper bound for the measure value.
unit - the unit for both the minimum and maximum values.
Returns:
the corresponding measure object.
Throws:
java.lang.IllegalArgumentException - if minimum > maximum

valueOf

public static Amount<?> valueOf(java.lang.CharSequence csq)
Returns the measure represented by the specified character sequence.

Parameters:
csq - the character sequence.
Returns:
AmountFormat.getInstance().parse(csq)

isExact

public boolean isExact()
Indicates if this measure amount is exact. An exact amount is guarantee exact only when stated in this measure unit (e.g. this.longValue()); stating the amount in any other unit may introduce conversion errors.

Returns:
true if this measure is exact; false otherwise.

getUnit

public Unit<Q> getUnit()
Returns the unit in which the estimated value and absolute error are stated.

Returns:
the measure unit.

getExactValue

public long getExactValue()
                   throws AmountException
Returns the exact value for this measure stated in this measure unit.

Returns:
the exact measure value (long) stated in this measure's unit
Throws:
AmountException - if this measure is not isExact()

getEstimatedValue

public double getEstimatedValue()
Returns the estimated value for this measure stated in this measure unit.

Returns:
the median value of the measure interval.

getMinimumValue

public double getMinimumValue()
Returns the lower bound interval value for this measure stated in this measure unit.

Returns:
the minimum value.

getMaximumValue

public double getMaximumValue()
Returns the upper bound interval value for this measure stated in this measure unit.

Returns:
the maximum value.

getAbsoluteError

public double getAbsoluteError()
Returns the value by which theestimated value may differ from the true value (all stated in base units).

Returns:
the absolute error stated in base units.

getRelativeError

public double getRelativeError()
Returns the percentage by which the estimated amount may differ from the true amount.

Returns:
the relative error.

to

public <R extends Quantity> Amount<R> to(Unit<R> unit)
Returns the measure equivalent to this measure but stated in the specified unit. The returned measure may not be exact even if this measure is exact due to conversion errors.

Parameters:
unit - the unit of the measure to be returned.
Returns:
a measure equivalent to this measure but stated in the specified unit.
Throws:
ConversionException - if the current model does not allows for conversion to the specified unit.

opposite

public Amount<Q> opposite()
Returns the opposite of this measure.

Returns:
-this.

plus

public Amount<Q> plus(Amount that)
                                throws ConversionException
Returns the sum of this measure with the one specified.

Parameters:
that - the measure to be added.
Returns:
this + that.
Throws:
ConversionException - if the current model does not allows for these quantities to be added.

minus

public Amount<Q> minus(Amount that)
                                 throws ConversionException
Returns the difference of this measure with the one specified.

Parameters:
that - the measure to be subtracted.
Returns:
this - that.
Throws:
ConversionException - if the current model does not allows for these quantities to be subtracted.

times

public Amount<Q> times(long factor)
Returns this measure scaled by the specified exact factor (dimensionless).

Parameters:
factor - the scaling factor.
Returns:
this · factor.

times

public Amount<Q> times(double factor)
Returns this measure scaled by the specified approximate factor (dimensionless).

Parameters:
factor - the scaling factor.
Returns:
this · factor.

times

public Amount<? extends Quantity> times(Amount that)
Returns the product of this measure with the one specified.

Parameters:
that - the measure multiplier.
Returns:
this · that.

inverse

public Amount<? extends Quantity> inverse()
Returns the multiplicative inverse of this measure. If this measure is possibly zero, then the result is unbounded (]-infinity, +infinity[).

Returns:
1 / this.

divide

public Amount<Q> divide(long divisor)
Returns this measure divided by the specified exact divisor (dimensionless).

Parameters:
divisor - the exact divisor.
Returns:
this / divisor.
Throws:
java.lang.ArithmeticException - if this measure is exact and the specified divisor is zero.

divide

public Amount<Q> divide(double divisor)
Returns this measure divided by the specified approximate divisor (dimensionless).

Parameters:
divisor - the approximated divisor.
Returns:
this / divisor.

divide

public Amount<? extends Quantity> divide(Amount that)
Returns this measure divided by the one specified.

Parameters:
that - the measure divisor.
Returns:
this / that.

abs

public Amount<Q> abs()
Returns the absolute value of this measure.

Returns:
|this|.

sqrt

public Amount<? extends Quantity> sqrt()
Returns the square root of this measure.

Returns:
sqrt(this)

root

public Amount<? extends Quantity> root(int n)
Returns the given root of this measure.

Parameters:
n - the root's order (n != 0).
Returns:
the result of taking the given root of this quantity.
Throws:
java.lang.ArithmeticException - if n == 0.

pow

public Amount<? extends Quantity> pow(int exp)
Returns this measure raised at the specified exponent.

Parameters:
exp - the exponent.
Returns:
thisexp

compareTo

public int compareTo(Measurable<Q> that)
Compares this measure with the specified measurable object.

Specified by:
compareTo in interface java.lang.Comparable<Measurable<Q extends Quantity>>
Parameters:
that - the measure to compare with.
Returns:
a negative integer, zero, or a positive integer as this measure is less than, equal to, or greater than that measurable.
Throws:
ConversionException - if the current model does not allows for these measure to be compared.

equals

public boolean equals(java.lang.Object that)
Compares this measure against the specified object for strict equality (same value interval and same units).

Overrides:
equals in class java.lang.Object
Parameters:
that - the object to compare with.
Returns:
true if this measure is identical to that measure; false otherwise.

hashCode

public int hashCode()
Returns the hash code for this measure.

Overrides:
hashCode in class java.lang.Object
Returns:
the hash code value.

approximates

public boolean approximates(Amount that)
Indicates if this measure approximates that measure. Measures are considered approximately equals if their value intervals overlaps. It should be noted that less accurate measurements are more likely to be approximately equals. It is therefore recommended to ensure that the measurement error is not too large before testing for approximate equality.

Returns:
this ≅ that

isLessThan

public boolean isLessThan(Amount<Q> that)
Indicates if this measure is ordered before that measure (independently of the measure unit).

Returns:
this.compareTo(that) < 0.

isGreaterThan

public boolean isGreaterThan(Amount<Q> that)
Indicates if this measure is ordered after that measure (independently of the measure unit).

Returns:
this.compareTo(that) > 0.

isLargerThan

public boolean isLargerThan(Amount<Q> that)
Compares this measure with that measure ignoring the sign.

Returns:
|this| > |that|

toText

public javolution.text.Text toText()
Returns the text representation of this measure.

Returns:
AmountFormat.getInstance().format(this)

toString

public final java.lang.String toString()
Returns the text representation of this amount as a java.lang.String.

Overrides:
toString in class java.lang.Object
Returns:
toText().toString()

doubleValue

public double doubleValue(Unit<Q> unit)
Description copied from interface: Measurable
Returns the value of this measurable stated in the specified unit as a double. If the measurable has too great a magnitude to be represented as a double, it will be converted to Double.NEGATIVE_INFINITY or Double.POSITIVE_INFINITY as appropriate.

Specified by:
doubleValue in interface Measurable<Q extends Quantity>
Parameters:
unit - the unit in which this measurable value is stated.
Returns:
the numeric value after conversion to type double.

longValue

public final long longValue(Unit<Q> unit)
Description copied from interface: Measurable
Returns the estimated integral value of this measurable stated in the specified unit as a long.

Note: This method differs from the Number.longValue() in the sense that the closest integer value is returned and an ArithmeticException is raised instead of a bit truncation in case of overflow (safety critical).

Specified by:
longValue in interface Measurable<Q extends Quantity>
Parameters:
unit - the unit in which the measurable value is stated.
Returns:
the numeric value after conversion to type long.

copy

public Amount<Q> copy()