uk.me.nxg.unity
Class OneUnit

java.lang.Object
  extended by uk.me.nxg.unity.OneUnit
Direct Known Subclasses:
FunctionOfUnit, SimpleUnit

public abstract class OneUnit
extends Object

A single unit.

The class's instances are immutable.


Method Summary
abstract  UnitDefinition getBaseUnitDefinition()
          Returns the known base unit.
abstract  String getBaseUnitName()
          Returns the name of this unit.
abstract  String getBaseUnitString()
          Returns the base unit string, which will only be non-null if this unit was an unrecognised one.
abstract  Dimensions getDimensions()
          Return the dimensions of the unit, if it is a recognised one.
 float getExponent()
          Obtains the power the unit is raised to.
abstract  int getPrefix()
          Returns the prefix of the unit, as a base-ten log.
abstract  boolean isRecognisedUnit(String syntax)
          Indicates whether the base unit is one of those recognised within the specification of the given syntax.
abstract  boolean isRecommendedUnit(String syntax)
          Indicates whether the base unit is one of those recommended within the specification of the given syntax.
abstract  boolean satisfiesUsageConstraints(String syntax)
          Indicates whether the unit is being used in a way which satisfies any usage constraints.
abstract  String toDebugString()
          Write out the unit in a testable format.
abstract  String toString()
          Format this unit in some sort of canonical form.
abstract  String toString(String syntax)
          Format this unit in some sort of canonical form appropriate to the given syntax.
abstract  String unitString(String syntaxName)
          Obtains the string representation of the unit, including prefix, in the given syntax.
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Method Detail

getPrefix

public abstract int getPrefix()
Returns the prefix of the unit, as a base-ten log. Thus a prefix of "m", for "milli", would produce a prefix of -3.


getBaseUnitDefinition

public abstract UnitDefinition getBaseUnitDefinition()
Returns the known base unit. If the unit wasn't recognised as a known unit in the syntax in which the string was parsed, then this returns null, though getBaseUnitString() will not.

Note that the 'base unit' is simply the unit without the prefix, and doesn't refer to the fundamental SI base units. Thus in the expression "MW", it is 'W', Watt, that is the base unit.


getBaseUnitName

public abstract String getBaseUnitName()
Returns the name of this unit. If the unit is a known one, then this will return a name for the unit such as 'Metre', or 'Julian year'; if it is not, then this can do no more than return the unit symbol.


getBaseUnitString

public abstract String getBaseUnitString()
Returns the base unit string, which will only be non-null if this unit was an unrecognised one. This is non-private because UnitExpr needs to know this when it's searching for units in the expression; it's package-only because this is not how clients should format units -- they should use the UnitExpr formatting facilities instead.


getDimensions

public abstract Dimensions getDimensions()
Return the dimensions of the unit, if it is a recognised one. If this isn't a recognised unit, return null.

Returns:
the dimensions of the unit, or null if these aren't avaiable

getExponent

public float getExponent()
Obtains the power the unit is raised to. For example, for the unit 'mm^2', return 2.


isRecognisedUnit

public abstract boolean isRecognisedUnit(String syntax)
Indicates whether the base unit is one of those recognised within the specification of the given syntax. In this context, "recognised" means "mentioned in the specification", so deprecated units count as recognised ones.

Note that this checks that the unit is a recommended one: we don't (currently) check whether the abbreviation that got us here is a recommended one (for example, "pixel" is a valid FITS/CDS name for pixels, and "pix" is a FITS and OGIP one).

Parameters:
syntax - one of the syntaxes of UnitParser
See Also:
isRecommendedUnit(java.lang.String)

isRecommendedUnit

public abstract boolean isRecommendedUnit(String syntax)
Indicates whether the base unit is one of those recommended within the specification of the given syntax. In this context, "recommended" means "mentioned in the specification" and not deprecated.

Note that this checks that the unit is a recommended one: we don't (currently) check whether the abbreviation that got us here is a recommended one (for example, "pixel" is a valid FITS/CDS name for pixels, and "pix" is a FITS and OGIP one).

Parameters:
syntax - one of the syntaxes of UnitParser
See Also:
isRecognisedUnit(java.lang.String)

satisfiesUsageConstraints

public abstract boolean satisfiesUsageConstraints(String syntax)
Indicates whether the unit is being used in a way which satisfies any usage constraints. Principally, this tests whether a unit which may not be used with SI prefixes was provided with a prefix, but there may be other constraints present.

An unrecognised unit has no constraints, and so will always satisfy them; this extends to units which are unrecognised in a particular syntax.

Parameters:
syntax - one of the syntaxes of UnitParser

toString

public abstract String toString()
Format this unit in some sort of canonical form. The form is unspecified. This should not generally be used for formatted output -- for that, it will generally be more appropriate to use UnitExpr.toString().

Overrides:
toString in class Object

toString

public abstract String toString(String syntax)
Format this unit in some sort of canonical form appropriate to the given syntax. The form is unspecified. This should not generally be used for formatted output -- for that, it will generally be more appropriate to use UnitExpr.toString().


unitString

public abstract String unitString(String syntaxName)
                           throws UnitParserException
Obtains the string representation of the unit, including prefix, in the given syntax. That is, return 'mm' not 'm' or 'metre'.

Parameters:
syntaxName - one of the syntaxes of UnitParser
Returns:
a non-null string representation of the unit
Throws:
UnitParserException - if the syntax is unrecognised

toDebugString

public abstract String toDebugString()
Write out the unit in a testable format. This is for debugging and testing.