javax.microedition.sensor
Class Unit

java.lang.Object
  javax.microedition.sensor.Unit

public class Unit
extends java.lang.Object

The Unit represents the unit of the measured data values. This class has a static factory method for creating new Unit instances. The factory method MUST always return the same object when the same symbol is passed in.

Naming

Symbols and names of units and related quantities are listed in the following tables. The aim is to promote the usage of internationally accepted and standardized units, thus SI units and derivatives are listed here in the first two tables. Also the most common convenience units (mainly English) are listed. The last table is for convenience units.

When using any of the listed units, the corresponding symbol from the table MUST be passed to the factory method exactly alike. If new symbols are needed, the symbol MUST be chosen to be unique by prefixing the unit symbol with the same inverted domain name that is used in naming Java packages, for example:

 private static final Unit COWS_PER_SECOND = Unit
                .getUnit("com.some_company.cow/s");
 

However, there is an exception to the rule: if the unit is well known and the its abbreviation is well established and not ambiguous, the name can be used as such, for example:

 private static final Unit NMI = Unit.getUnit("nmi"); //nautical-mile
 

The format of unit symbols follows C programming language conventions and mathematical operators, short summary here:

Add	+
Divide	/
Multiply	*
Power	^
Subtract	-

Parentheses are used if the order of operations is otherwise unclear, for example, the symbol for "joule per kilogram kelvin" is "J/(kg*K)".

Scaling

One thing to notice is scaling. The scaling factor can be obtained from ChannelInfo with the method ChannelInfo.getScale(). The scaling factor, which differs from 0, has notable effect on how data values are interpreted, see definition of ChannelInfo.getScale() for more details. Basic units and scaling MUST be used instead of adding SI prefixes (such as nano, milli, and kilo) to units. For example, instead of using milliseconds ("ms") and scaling factor 0, basic unit second ("s") MUST be used with the scaling factor -3.

Relation to quantity

Related quantities are listed in the third column of the tables. The relation of the unit to the quantity is a many-to-many relationship. For example, pascal, the unit of pressure, can be used as the unit of pressure or stress. The temperature quantity has many unit alternatives: kelvin, degree Celsius, or Fahrenheit. If there are many quantities listed for one unit in the tables below, the quantities are separated with "/".

SI units

Symbol	Name	Quantity
A	ampere	electric_current
Bq	becquerel	activity
C	coulomb	electric_charge
cd	candela	luminous_intensity
Celsius	degree Celsius	temperature
F	farad	capacitance
Gy	gray	absorbed_dose/specific_energy/kerma
H	henry	inductance
Hz	hertz	frequency
J	joule	energy/work/quantity_of_heat
K	kelvin	temperature
kat	katal	catalytic_activity
kg	kilogram	mass
lm	lumen	luminous_flux
lx	lux	illuminance
m	meter	length
mol	mole	amount_of_substance
N	newton	force
ohm	ohm	electric_resistance
Pa	pascal	pressure/stress
rad	radian	plane_angle
s	second	time/duration
S	siemens	electric_conductance
sr	steradian	solid_angle
Sv	sievert	dose_equivalent
T	tesla	magnetic_flux_density
V	volt	electric_potential_difference
W	watt	power/radiant_flux
Wb	weber	magnetic_flux

SI unit derivates

Symbol	Name	Quantity
m^-1	reciprocal meter	wave_number
A/m	ampere per meter	magnetic_field_strength
A/m^2	ampere per square meter	current_density
C/kg	coulomb per kilogram	exposure
C/m^2	coulomb per square meter	electric_flux_density
C/m^3	coulomb per cubic meter	electric_charge_density
cd/m^2	candela per square meter	luminance
F/m	farad per meter	permittivity
Gy/s	gray per second	absorbed_dose_rate
H/m	henry per meter	permeability
J/(kg*K)	joule per kilogram kelvin	specific_heat_capacity/specific_entropy
J/(mol*K)	joule per mole kelvin	molar_entropy/molar_heat_capacity
J/K	joule per kelvin	heat_capacity/entropy
J/kg	joule per kilogram	specific_energy
J/m^3	joule per cubic meter	energy_density
J/mol	joule per mole	molar_energy
kat/m^3	katal per cubic meter	catalytic_concentration
kg/m^3	kilogram per cubic meter	mass_density
m/s	meter per second	velocity
m/s^2	meter per square second	acceleration
m^2	square meter	area
m^3	cubic meter	volume
m^3/kg	cubic meter per kilogram	specific_volume
mol/m^3	mol per cubic meter	amount_of_substance_concentration
N*m	newton meter	moment_of_force
N/m	newton per meter	surface_tension
Pa*s	pascal second	dynamic_viscosity
rad/s	radian per second	angular_velocity
rad/s2	radian per second squared	angular_acceleration
W/(m*K)	watt per meter kelvin	thermal_conductivity
W/(m^2*sr)	watt per square meter steradian	radiance
V/m	volt per meter	electric_field_strength
W/m^2	watt per square meter	heat_flux_density/irradiance
W/sr	watt per steradian	radiant_intensity

Convenience units

Symbol	Name	Quantity
atm	atmosphere	pressure/stress
bar	bar	pressure/stress
bpm	beats per minute	heart_rate
boolean	boolean	logical_value
byte	byte	data_size
cal	calorie	energy
degree	degree	plane_angle
Fahrenheit	Fahrenheit	temperature
ft	foot	length
G	gravitational constant	acceleration
hp	horsepower	power
in	inch	length
lb	pound	mass
mi	mile	length
mmHg	millimeter of mercury	pressure/blood_pressure
oz	ounce	mass
%	percent	percentage
pixel	pixel	length
yd	yard	length
unit	unit	unit

Method Summary

static Unit	getUnit(java.lang.String symbol) The method returns the Unit that matches the given symbol.
java.lang.String	toString() Returns the symbol of the Unit

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Method Detail

getUnit

public static Unit getUnit(java.lang.String symbol)

The method returns the Unit that matches the given symbol. The given symbol can be one of the listed symbols or a new one. All new symbols MUST follow the format stated in the class description. The returned object MUST be the same for every request with the same symbol.

Parameters:

symbol - the symbol of the unit

Returns:

Unit with the given symbol

Throws:

java.lang.NullPointerException - if the symbol is null

java.lang.IllegalArgumentException - if the symbol is empty string

toString

public java.lang.String toString()

Returns the symbol of the Unit

Overrides:

toString in class java.lang.Object

Returns:

the symbol of the Unit