Unit Class Reference

A Unit is a combination of base unit terms, with a preferred power of 1000 multiple of the base unit for each term. More...

List of all members.

Public Member Functions
	Unit ()
	Default constructor.
	Unit (String unitstr) throws HDUnitException
	Constructor from string.
	Unit (Unit other)
	Copy constructor.
	Unit (UnitTerm term)
	Constructor from UnitTerm.
	Unit (Collection< UnitTerm > terms)
	Constructor from UnitTerms.
	Unit (UnitTerm terms[])
	Constructor from UnitTerms.
List< UnitTerm >	getUnitTerms ()
	Get the list of UnitTerms.
void	setUnitTerms (List< UnitTerm > unitTerms)
	Set the list of UnitTerms.
void	addUnitTerm (UnitTerm unitTerm)
	Add an entry to the list of UnitTerms.
boolean	equals (Object obj)
	Is this Unit equivalent to another one?
Unit	canonicalUnit ()
	Return the canonical (i.e.
Double	convFactorToCanonical ()
	Get the conversion factor from this Unit *to* its canonical representation.
Double	convFactorFromCanonical ()
	Get the conversion factor to this unit *from* its canonical representation.
boolean	isCompatible (Unit unit)
	Determine whether this unit can be converted to the supplied unit and vice versa.
Double	convFactorTo (Unit unit) throws HDUnitException
	Deduce the conversion factor from this Unit to the supplied Unit.
Double	convFactorFrom (Unit unit) throws HDUnitException
	Deduce the conversion factor to this Unit from the supplied Unit.
String	toString ()
	Provide string representation of this unit.
Unit	fromString (String unitstr) throws HDUnitException
	Populate a Unit object from a string.
Static Public Member Functions
static Unit	makeGeV ()
static Unit	makeGeVc ()
static Unit	makeGeVcsq ()
Static Package Attributes
static Logger	log = Logger.getLogger(Unit.class)

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Detailed Description

A Unit is a combination of base unit terms, with a preferred power of 1000 multiple of the base unit for each term.

Every Axis has a corresponding Unit. Any given Unit has a canonical representation, which is the form in which measurement values stored with that Unit will be stored in the database. The Unit associated with an Axis is the form in which values associated with that axis will be represented in HTML, plain text, XML, etc. output.

Be warned: this class is not intended to provide a "proper" reduction of units to their SI (or other) base units, as combining that with the HepData need to reproduce data in the form preferred by the reporting experiment would probably be fiddly. So, don't try converting between eV and m^-1, for example: we don't attempt to recognise that they are compatible units (and certainly not with the appropriate invisible power of c_light). The fact that this is a fiddly thing to do makes the author even more impressed by the Google calculator!

Todo:

Do c_light and number factors get seamlessly handled? (They should do.)

Todo:

Do we need to deal with subdivisions for degree into arcmin and arcsec? (See http://en.wikipedia.org/wiki/Arcsecond)

Author:

Andy Buckley

Version:

Id

Unit.java 1004 2007-06-07 15:36:26Z buckley

Definition at line 35 of file Unit.java.

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Constructor & Destructor Documentation

Unit

(

)

Default constructor.

Definition at line 46 of file Unit.java.

Referenced by Unit.canonicalUnit(), and Unit.makeGeV().

{}

Unit

(

String

unitstr

)

throws HDUnitException

Constructor from string.

Definition at line 49 of file Unit.java.

                                                       {
        this.fromString(unitstr);
    }

Unit

(

Unit

other

)

Copy constructor.

Definition at line 54 of file Unit.java.

References Unit.getUnitTerms().

                            {
        for (UnitTerm term : other.getUnitTerms()) {
            this.addUnitTerm(new UnitTerm(term.baseunit, term.prefix, term.power));
        }
    }

Unit

(

UnitTerm

term

)

Constructor from UnitTerm.

Definition at line 61 of file Unit.java.

                               {
        this.addUnitTerm(term);
    }

Unit

(

Collection< UnitTerm >

terms

)

Constructor from UnitTerms.

Definition at line 66 of file Unit.java.

                                            {
        for (UnitTerm term : terms) {
            this.addUnitTerm(term);
        }
    }

Unit

(

UnitTerm

terms[]

)

Constructor from UnitTerms.

Definition at line 73 of file Unit.java.

                                  {
        for (UnitTerm term : terms) {
            this.addUnitTerm(term);
        }
    }

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Member Function Documentation

static Unit makeGeV

(

)

[static]

Definition at line 84 of file Unit.java.

References Unit.Unit().

Referenced by Unit.makeGeVc(), and Unit.makeGeVcsq().

                                 {
        return new Unit(new UnitTerm(BaseUnit.EV, SiPrefix.GIGA, 1));
    }

static Unit makeGeVc

(

)

[static]

Definition at line 87 of file Unit.java.

References Unit.addUnitTerm(), and Unit.makeGeV().

                                  {
        Unit gevc = makeGeV();
        gevc.addUnitTerm(new UnitTerm(BaseUnit.CLIGHT, SiPrefix.UNIT, -1));
        return gevc;
    }

static Unit makeGeVcsq

(

)

[static]

Definition at line 92 of file Unit.java.

References Unit.addUnitTerm(), and Unit.makeGeV().

                                    {
        Unit gevcsq = makeGeV();
        gevcsq.addUnitTerm(new UnitTerm(BaseUnit.CLIGHT, SiPrefix.UNIT, -2));
        return gevcsq;
    }

List<UnitTerm> getUnitTerms

(

)

Get the list of UnitTerms.

Definition at line 103 of file Unit.java.

Referenced by Unit.canonicalUnit(), Unit.convFactorTo(), Unit.convFactorToCanonical(), Unit.equals(), Unit.isCompatible(), Unit.toString(), and Unit.Unit().

                                         {
        return unitTerms;
    }

void setUnitTerms

(

List< UnitTerm >

unitTerms

)

Set the list of UnitTerms.

Todo:

Should this be more careful about references vs. values?

Definition at line 109 of file Unit.java.

                                                       {
        this.unitTerms = unitTerms;
    }

void addUnitTerm

(

UnitTerm

unitTerm

)

Add an entry to the list of UnitTerms.

Definition at line 114 of file Unit.java.

Referenced by Unit.canonicalUnit(), Unit.fromString(), Unit.makeGeVc(), and Unit.makeGeVcsq().

                                               {
        this.unitTerms.add(unitTerm);
    }

boolean equals

(

Object

obj

)

Is this Unit equivalent to another one?

Definition at line 119 of file Unit.java.

References Unit.getUnitTerms().

Referenced by Unit.convFactorTo(), and Unit.isCompatible().

                                      {
        if (this == obj) return true;
        if (! (obj instanceof Unit)) return false;

        Unit test = (Unit) obj;
        List<UnitTerm> terms1 = getUnitTerms();
        List<UnitTerm> terms2 = test.getUnitTerms();
        if (terms1.size() != terms2.size()) return false;

        for (int i = 0; i < terms1.size(); ++i) {
            if (! terms1.get(i).equals(terms2.get(i)) ) return false;
        }
        return true;
    }

Unit canonicalUnit

(

)

Return the canonical (i.e.

storage units for this Unit).

Definition at line 135 of file Unit.java.

References Unit.addUnitTerm(), Unit.getUnitTerms(), UnitTerm.prefix, and Unit.Unit().

Referenced by Unit.convFactorTo(), and Unit.isCompatible().

                                {
        Unit cu = new Unit();
        for (UnitTerm term : getUnitTerms()) {
            UnitTerm cterm = new UnitTerm(term.baseunit, term.prefix, term.power);
            cterm.prefix = SiPrefix.UNIT;
            cu.addUnitTerm(cterm);
        }
        return cu;
    }

Double convFactorToCanonical

(

)

Get the conversion factor from this Unit *to* its canonical representation.

Definition at line 146 of file Unit.java.

References Unit.getUnitTerms().

Referenced by Unit.convFactorFromCanonical(), and Unit.convFactorTo().

                                          {
        Double cf = 1.0;
        for (UnitTerm term : getUnitTerms()) {
            cf *= term.convFactor();
        }
        return cf;
    }

Double convFactorFromCanonical

(

)

Get the conversion factor to this unit *from* its canonical representation.

Definition at line 155 of file Unit.java.

References Unit.convFactorToCanonical().

                                            {
        return 1.0 / convFactorToCanonical();
    }

boolean isCompatible

(

Unit

unit

)

Determine whether this unit can be converted to the supplied unit and vice versa.

Definition at line 160 of file Unit.java.

References Unit.canonicalUnit(), Unit.equals(), Unit.getUnitTerms(), and Unit.log.

Referenced by Unit.convFactorTo().

                                           {
        Unit myCU = canonicalUnit();
        Unit otherCU = unit.canonicalUnit();

        // First test if their canonical representations are the same: it
        // makes things a lot easier if they are!
        if ( myCU.equals(otherCU) ) return true;

        // If they aren't exactly equal, eliminate matching elements from each
        // list and then see what's left over. First we have to make independent
        // copies of the term lists which we can mangle:
        List<UnitTerm> terms1 = new Vector<UnitTerm>();
        List<UnitTerm> terms2 = new Vector<UnitTerm>();
        for (UnitTerm term : myCU.getUnitTerms()) { terms1.add(new UnitTerm(term)); }
        for (UnitTerm term : otherCU.getUnitTerms()) { terms2.add(new UnitTerm(term)); }

        // Now strip out the stuff that matches from terms1
        for (UnitTerm term2 : otherCU.getUnitTerms()) {
            for (UnitTerm term1 : terms1) {
                log.debug(term1 + "-" + term2 + ": " + term2.equals(term1));
                if (term2.equals(term1)) {
                    terms1.remove(term1);
                    break;
                }
            }
        }
        // Now strip out the stuff that matches from terms2
        for (UnitTerm term1 : myCU.getUnitTerms()) {
            for (UnitTerm term2 : terms2) {
                log.debug(term2 + "-" + term1 + ": " + term1.equals(term2));
                if (term1.equals(term2)) {
                    terms2.remove(term2);
                    break;
                }
            }
        }
        log.info("T1: " + myCU.getUnitTerms() + " -> " + terms1);
        log.info("T2: " + otherCU.getUnitTerms() + " -> " + terms2);

        // Seeing what's left over: if it isn't a c_light, number or rad/deg
        // then it's incompatible. We also remove c_light and number on this pass,
        // so that we can match up rad/deg elements next...
        for (UnitTerm term : terms1) {
            if (term.baseunit.equals(BaseUnit.NUMBER) || term.baseunit.equals(BaseUnit.CLIGHT)) {
                terms1.remove(term);
            } else if (term.baseunit.equals(BaseUnit.RADIAN) || term.baseunit.equals(BaseUnit.DEGREE)) {
                log.info("Found a remaining angular unit: " + term.toString());
            } else {
                return false;
            }
        }
        for (UnitTerm term : terms2) {
            if (term.baseunit.equals(BaseUnit.NUMBER) || term.baseunit.equals(BaseUnit.CLIGHT)) {
                terms2.remove(term);
            } else if (term.baseunit.equals(BaseUnit.RADIAN) || term.baseunit.equals(BaseUnit.DEGREE)) {
                log.info("Found a remaining angular unit: " + term.toString());
            } else {
                return false;
            }
        }
        if (terms1.size() == 0 && terms2.size() == 0) return true;
        if (terms1.size() != terms2.size()) return false;

        // Try to match up remaining elements: check that the summed powers of angular
        // units are the same for both units
        int angPower1 = 0;
        int angPower2 = 0;
        for (UnitTerm t : terms1) angPower1 += t.power;
        for (UnitTerm t : terms2) angPower2 += t.power;
        if (angPower1 != angPower2) return false;

        // Finally, the units must be compatible (at last!)
        return true;
    }

Double convFactorTo

(

Unit

unit

)

throws HDUnitException

Deduce the conversion factor from this Unit to the supplied Unit.

Todo:

Handle degrees, radians etc.

Definition at line 236 of file Unit.java.

References Unit.canonicalUnit(), Unit.convFactorToCanonical(), Unit.equals(), Unit.getUnitTerms(), Unit.isCompatible(), Unit.log, and Unit.toString().

Referenced by Unit.convFactorFrom().

                                                                 {
        if (isCompatible(unit)) {
            Double sifactor = convFactorToCanonical() * unit.convFactorFromCanonical();
            if (canonicalUnit().equals(unit.canonicalUnit())) {
                return sifactor;
            } else {
                int degPower1 = 0;
                for (UnitTerm t : this.getUnitTerms()) {
                    if (t.baseunit == BaseUnit.DEGREE) degPower1 += 1;
                    if (t.baseunit == BaseUnit.RADIAN) degPower1 -= 1;
                }
                int degPower2 = 0;
                for (UnitTerm t : unit.getUnitTerms()) {
                    if (t.baseunit == BaseUnit.DEGREE) degPower2 += 1;
                    if (t.baseunit == BaseUnit.RADIAN) degPower2 -= 1;
                }
                int deltaDegPower = degPower2 - degPower1;
                assert deltaDegPower % 2 == 0 : "Shift in number of powers of degree is not even. How?!?";
                log.debug(degPower1 + " -> " + degPower2 + " so shift is " + deltaDegPower);
                Double angfactor = Math.pow(180.0/Math.PI, deltaDegPower/2.0);
                return sifactor * angfactor;
            }
        } else {
            throw new HDUnitException("Units " + toString() + " and " + unit.toString() + " are not compatible");
        }
    }

Double convFactorFrom

(

Unit

unit

)

throws HDUnitException

Deduce the conversion factor to this Unit from the supplied Unit.

Definition at line 265 of file Unit.java.

References Unit.convFactorTo().

                                                                   {
        return 1.0/ convFactorTo(unit);
    }

String toString

(

)

Provide string representation of this unit.

Definition at line 270 of file Unit.java.

References Unit.getUnitTerms().

Referenced by Unit.convFactorTo().

                             {
        StringBuffer s = new StringBuffer();
        for (UnitTerm term : getUnitTerms()) {
            s.append(term.toString());
            s.append(" ");
        }
        return s.toString().trim();
    }

Unit fromString

(

String

unitstr

)

throws HDUnitException

Populate a Unit object from a string.

Definition at line 280 of file Unit.java.

References Unit.addUnitTerm(), and Unit.log.

                                                                  {
        unitTerms.clear();
        String myunitstr = unitstr;
        if (myunitstr.length() == 0) {
            return this;
        }

        // Replace ** with ^, replace " *\* *" with " ", replace " */ *" with " /"
        myunitstr = myunitstr.replaceAll("\\*\\*", "^");
        log.debug("1. " + unitstr + " vs. " + myunitstr);
        myunitstr = myunitstr.replaceAll("\\ *\\*\\ *", " ");
        log.debug("2. " + unitstr + " vs. " + myunitstr);
        myunitstr = myunitstr.replaceAll("\\ */\\ *", " /");
        log.debug("3. " + unitstr + " vs. " + myunitstr);

        String[] unitatoms = myunitstr.split(" ");
        for (String atom : unitatoms) {
            UnitTerm term = new UnitTerm(atom);
            addUnitTerm(term);
        }
        return this;
    }

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Member Data Documentation

Logger log = Logger.getLogger(Unit.class) [static, package]

Definition at line 36 of file Unit.java.

Referenced by Unit.convFactorTo(), Unit.fromString(), and Unit.isCompatible().

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The documentation for this class was generated from the following file:

• /home/buckley/hepdata/codedocs/src/hepdata/hepdata-common/src/main/java/cedar/hepdata/util/Unit.java