Package javax.measure

Provides strongly typed measurements to enforce compile-time check of parameters consistency and avoid interface errors.


Interface Summary
Measurable<Q extends Quantity> This interface represents the measurable, countable, or comparable property or aspect of a thing.

Class Summary
DecimalMeasure<Q extends Quantity> This class represents a measure whose value is an arbitrary-precision decimal number.
Measure<V,Q extends Quantity> This class represents the result of a measurement stated in a known unit.
MeasureFormat This class provides the interface for formatting and parsing measures.
VectorMeasure<Q extends Quantity> This class represents a measurement vector of two or more dimensions.

Package javax.measure Description

Provides strongly typed measurements to enforce compile-time check of parameters consistency and avoid interface errors.

Let's take the following example:[code] class Person { void setWeight(double weight); }[/code] Should the weight be in pound, kilogram ??
Using measures there is no room for error:[code] class Person { void setWeight(Measurable weight); }[/code] Not only the interface is cleaner (the weight has to be of mass type); but also there is no confusion on the measurement unit:[code] double weightInKg = weight.doubleValue(KILOGRAM); double weightInLb = weight.doubleValue(POUND);[/code] Measurable work hand-in-hand with units (also parameterized). For example, the following would result in compile-time error:[code] double weightInLiter = weight.doubleValue(LITER); // Compile error, Unit required. [/code]

Users may create their own Measurable implementation:[code] public class Period implements Measurable { long nanoseconds; ... } public class Distance implements Measurable { double meters; ... } public class Velocity3D implements Measurable { double x, y, z; // In meters. ... } [/code]

Users may also combine a definite amount (scalar, vector, collection, etc.) to a unit and make it a Measure (and a Measurable instance). For example: [code] // Scalar measurement (numerical). person.setWeight(Measure.valueOf(180.0, POUND)); // Measure timer.setPeriod(Measure.valueOf(20, MILLI(SECOND)); // Measure circuit.setCurrent(Measure.valueOf(Complex.valueOf(2, -3), AMPERE); // (2 - 3i) A bottle.setPression(Measure.valueOf(Rational.valueOf(20, 100), ATMOSPHERE)); // (20/100) Atm // Vector measurement. abstract class MeasureVector extends Measure { ... // doubleValue(Unit) returns vector norm. } MeasureVector v = MeasureVector.valueOf(METRE_PER_SECOND, 1.0, 2.0, 3.0); plane.setVelocity(v); // Statistical measurement. class Average extends Measure{ ... // doubleValue(Unit) returns average value. } sea.setTemperature(Average.valueOf(new double[] { 33.4, 44.55, 32.33} , CELCIUS)); // Measurement with uncertainty (and additional operations). public class Amount extends Measurable { public Amount(double value, double error, Unit unit) { ... } public Amount plus(Amount that) {...} public Amount times(Amount that) {...} ... // doubleValue(Unit) returns estimated value. } [/code]