* *
This class only support exponents for the base SI units in the range -64 to +63. * Any operation which produces an exponent outside of this range will result in * a Unit object with undefined exponents. * * @version $Revision: 1.1.1.1 $ * @author Open Services Gateway Initiative */ /* * This local class maintains the information about units. * It can calculate new units when two values are multiplied, * divided, added or subtracted. *
* The unit works with the 7 basic SI types + rad + * up to 2^6 custom types. For each type, the unit keeps * a bit mask with the exponents of the basic types. Eg. m/s is * m = 1, s = -1. Multiplying one unit with another means * that the bit masks are added, dividing means that the bit masks * are subtracted. *
* This class can handle any reasonable combination of SI * units. However, it will always try to coerce results back * into the basic set. E.g. when you do V*A you should get * W and not m2.kg/s3 . Only when the existing types do not * match does the unit fallback to the expanded form. *
* This class uses offset arithmetic. * This means that the exponents are stored in an long. * The special field is used for units that should not * be arithmetically divided or multiplied, like longitude * and lattitude. These special units can however, be divided and multiplied * by the basic 7 constants of the SI, e.g. deg/s. */ public class Unit { private final static long UNITY = createType(0,0,0,0,0,0,0,0,0); private final static long ZERO = 0x40L; private final static long MASK = 0x7fL; private final static int m_SHIFT = 0; private final static int s_SHIFT = 7; private final static int kg_SHIFT = 14; private final static int K_SHIFT = 21; private final static int A_SHIFT = 28; private final static int mol_SHIFT = 35; private final static int cd_SHIFT = 42; private final static int rad_SHIFT = 49; private final static int x_SHIFT = 56; private final static long m_MASK = MASK << m_SHIFT; private final static long s_MASK = MASK << s_SHIFT; private final static long kg_MASK = MASK << kg_SHIFT; private final static long K_MASK = MASK << K_SHIFT; private final static long A_MASK = MASK << A_SHIFT; private final static long mol_MASK = MASK << mol_SHIFT; private final static long cd_MASK = MASK << cd_SHIFT; private final static long rad_MASK = MASK << rad_SHIFT; private final static long x_MASK = MASK << x_SHIFT; /** No Unit (Unity) */ public final static Unit unity = new Unit( "", UNITY); // Unity /* SI Base Units */ /** The length unit meter (m) */ public final static Unit m = new Unit("m", createType(0,0,0,0,0,0,0,0,1)); // Distance meter /** The time unit second (s) */ public final static Unit s = new Unit("s", createType(0,0,0,0,0,0,0,1,0)); // Time Seconds s /** The mass unit kilogram (kg) */ public final static Unit kg = new Unit("kg", createType(0,0,0,0,0,0,1,0,0)); // Mass kilogram kg /** The temperature unit kelvin (K) */ public final static Unit K = new Unit("K", createType(0,0,0,0,0,1,0,0,0)); // Temperature kelvin K /** The electric current unit ampere (A) */ public final static Unit A = new Unit("A", createType(0,0,0,0,1,0,0,0,0)); // Current ampere A /** The amount of substance unit mole (mol) */ public final static Unit mol = new Unit("mol", createType(0,0,0,1,0,0,0,0,0)); // Substance mole mol /** The luminous intensity unit candela (cd) */ public final static Unit cd = new Unit("cd", createType(0,0,1,0,0,0,0,0,0)); // Light candela cd /* SI Derived Units */ /** The speed unit meter per second (m/s) */ public final static Unit m_s = new Unit("m/s", createType(0,0,0,0,0,0,0,-1,1)); // Speed m/s /** The acceleration unit meter per second squared (m/s2) */ public final static Unit m_s2 = new Unit("m/s2",createType(0,0,0,0,0,0,0,-2,1)); // Acceleration m/s^2 /** The area unit square meter(m2) */ public final static Unit m2 = new Unit("m2", createType(0,0,0,0,0,0,0,0,2)); // Surface m^2 /** The volume unit cubic meter (m3) */ public final static Unit m3 = new Unit("m3", createType(0,0,0,0,0,0,0,0,3)); // Volume m^3 /** The frequency unit hertz (Hz).
hertz is expressed in SI units as 1/s */ public final static Unit Hz = new Unit("Hz", createType(0,0,0,0,0,0,0,-1,0)); // Frequency 1/s /** The force unit newton (N).
N is expressed in SI units as m·kg/s2 */ public final static Unit N = new Unit("N", createType(0,0,0,0,0,0,1,-2,1)); // Force newton (m*kg)/s^2 /** The pressure unit pascal (Pa).
Pa is equal to N/m2 or is expressed in SI units as kg/m·s2 */ public final static Unit Pa = new Unit("Pa", createType(0,0,0,0,0,0,1,-2,-1)); // Pressure pascal kg/(m*s^2) /** The energy unit joule (J).
joule is equal to N·m
or is expressed in SI units as m2·kg/s2 */
public final static Unit J = new Unit("J", createType(0,0,0,0,0,0,1,-2,2)); // Energy joule (m^2*kg)/s^2
/** The power unit watt (W).
watt is equal to J/s
or is expressed in SI units as m2·kg/s3 */
public final static Unit W = new Unit("W", createType(0,0,0,0,0,0,1,-3,2)); // Power watt (m^2*kg)/s^3
/** The electric charge unit coulomb (C).
coulomb is expressed in SI units as
s·A */
public final static Unit C = new Unit("C", createType(0,0,0,0,1,0,0,1,0)); // Charge coulumb s*A
/** The electric potential difference unit volt (V).
volt is equal to W/A
or is expressed in SI units as
m2·kg/s3·A */
public final static Unit V = new Unit("V", createType(0,0,0,0,-1,0,1,-3,2)); // El. Potent. volt (m^2*kg)/(s^3*A)
/** The capacitance unit farad (F).
farad is equal to C/V
or is expressed in SI units as
s4·A2/m2·kg */
public final static Unit F = new Unit("F", createType(0,0,0,0,2,0,-1,4,-2)); // Capacitance farad (s^4*A^2)/(m^2*kg)
/** The electric resistance unit ohm.
ohm is equal to V/A
or is expressed in SI units as
m2·kg/s3·A2 */
public final static Unit Ohm = new Unit("ohm", createType(0,0,0,0,-2,0,1,-3,2)); // Resistance ohm (m^2*kg)/(s^3*A^2)
/** The electric conductance unit siemens (S).
siemens is equal to A/V
or is expressed in SI units as
s3·A2/m2·kg */
public final static Unit S = new Unit("S", createType(0,0,0,0,2,0,-1,3,-2)); // Conductance siemens (s^3*A^2)/(m^2*kg)
/** The magnetic flux unit weber (Wb).
weber is equal to V·s
or is expressed in SI units as
m2·kg/s2·A */
public final static Unit Wb = new Unit("Wb", createType(0,0,0,0,-1,0,1,-2,2)); // Magn. Flux weber (m^2*kg)/(s^2*A)
/** The magnetic flux density unit tesla (T).
tesla is equal to Wb/m2
or is expressed in SI units as
kg/s2·A */
public final static Unit T = new Unit("T", createType(0,0,0,0,-1,0,1,-2,0)); // Magn. Flux Dens. tesla kg/(s^2*A)
/** The illuminance unit lux (lx).
lux is expressed in SI units as
cd/m2 */
public final static Unit lx = new Unit("lx", createType(0,0,1,0,0,0,0,0,-2)); // Illuminace lux cd/m^2
/** The absorbed dose unit gray (Gy).
Gy is equal to J/kg
or is expressed in SI units as m2/s2 */
public final static Unit Gy = new Unit("Gy", createType(0,0,0,0,0,0,0,-2,2)); // Absorbed dose gray m^2/s^2
/** The catalytic activity unit katal (kat).
katal is expressed in SI units as
mol/s */
public final static Unit kat = new Unit("kat", createType(0,0,0,1,0,0,0,-1,0)); // Catalytic Act. katal mol/s
/** The angle unit radians (rad) */
public final static Unit rad = new Unit("rad", createType(0,1,0,0,0,0,0,0,0)); // Angle radians rad
/** An array containing all units defined. The first seven items must be
* m, s, kg, K, A, mol, cd, rad in this order!
*/
private final static Unit [] allUnits = new Unit[] { m, s, kg, K, A, mol, cd, rad, m_s, m_s2, m2, m3, Hz, N, Pa, J, W, C, V, F, Ohm, S, Wb, T, lx, Gy, kat, unity};
private static Hashtable base;
private String name;
private long type;
/**
* Creates a new Unit instance.
*
* @param name the name of the Unit
* @param type the type of the Unit
*/
private Unit(String name, long type)
{
this.name = name;
this.type = type;
//System.out.println( name + " " + Long.toHexString( type ) );
}
/**
* Create a type field from the base SI unit exponent values.
*
*/
private static long createType(int x, int rad, int cd, int mol, int A, int K, int kg, int s, int m)
{
return (((ZERO + m)&MASK) << m_SHIFT) |
(((ZERO + s)&MASK) << s_SHIFT) |
(((ZERO + kg)&MASK) << kg_SHIFT) |
(((ZERO + K)&MASK) << K_SHIFT) |
(((ZERO + A)&MASK) << A_SHIFT) |
(((ZERO + mol)&MASK) << mol_SHIFT) |
(((ZERO + cd)&MASK) << cd_SHIFT) |
(((ZERO + rad)&MASK) << rad_SHIFT) |
(((long)x) << x_SHIFT);
}
/**
* Checks whether this Unit object is equal to the
* specified Unit object. The Unit objects
* are considered equal if their exponents are equal.
*
* @param obj the Unit object that should be checked
* for equality
*
* @return true if the specified Unit object is equal
* to this Unit object.
*/
public boolean equals(Object obj)
{
if (this == obj)
{
return true;
}
if (!(obj instanceof Unit))
{
return false;
}
return ((Unit)obj).type == type;
}
/**
* Returns the hash code for this object.
*
* @return This object's hash code.
*/
public int hashCode()
{
return (int)((type >>> 32) ^ type);
}
/**
* Returns a new Unit that is the multiplication of this
* Unit and the Unit specified
*
* @param that the Unit that will be multiplied with this Unit
*
* @return a new Unit that is the multiplication of this
* Unit and the Unit specified
*
* @exception RuntimeException if both Units are special
*
* @see Unit#isSpecial
*/
Unit mul(Unit that)
{
if (this.isSpecial() && that.isSpecial())
{
throw new ArithmeticException("Cannot multiply " + this + " with " + that);
}
return find(this.type - UNITY + that.type);
}
/**
* Returns a new Unit that is the division of this
* Unit and the Unit specified
*
* @param that the Unit that this Unit
* will be divided with
* @return a new Unit that is the division of this
* Unit and the Unit specified
*
* @exception RuntimeException if both Units are special
*
* @see Unit#isSpecial
*/
Unit div(Unit that)
{
if (this.isSpecial() && that.isSpecial())
{
if (this.type == that.type)
{
return Unit.unity;
}
throw new ArithmeticException("Cannot divide " + this + " by " + that);
}
return find(this.type - that.type + UNITY);
}
/**
* Returns a new Unit that is the addition of this
* Unit and the Unit specified.
*
* @param that the Unit that should be added to this Unit
*
* @return a new Unit that is the addition of this
* Unit and the Unit specified.
*
* @exception RuntimeException if the two Units are not the same
*/
Unit add(Unit that)
{
if (!this.equals(that))
{
throw new ArithmeticException("Cannot add " + this + " to " + that);
}
return this;
}
/**
* Returns a new Unit that is the subtraction between
* this Unit and the Unit specified.
*
* @param that the Unit that will be subtracted from this
* Unit
* @return a new Unit that is the subtraction between
* this Unit and the Unit specified.
*
* @return RuntimeException if the Unit specified is not the same
* as this Unit
*/
Unit sub(Unit that)
{
if (!this.equals(that))
{
throw new ArithmeticException("Cannot subtract " + that + " from " + this);
}
return this;
}
/**
* Finds a Unit based on a type. If the Unit
* is not found, it will be created and added to the list of all
* units under a null name.
*
* @param type the type of the Unit to find
*
* @return the Unit
*/
static Unit find(long type)
{
if (base == null)
{
synchronized(Unit.class)
{
if (base == null)
{
int size = allUnits.length;
base = new Hashtable(size << 1);
for (int i = 0; i < size; i++)
{
base.put(allUnits[i], allUnits[i]);
}
}
}
}
Unit unit = new Unit(null, type);
Unit out = (Unit) base.get(unit);
if (out == null)
{
base.put(unit, unit);
out = unit;
}
return out;
}
/**
* Returns a String object representing the Unit
*
* @return A String object representing the Unit
*/
public String toString()
{
if (name == null)
{
int m = (int) (((type >> m_SHIFT) & MASK) - ZERO);
int s = (int) (((type >> s_SHIFT) & MASK) - ZERO);
int kg = (int) (((type >> kg_SHIFT) & MASK) - ZERO);
int K = (int) (((type >> K_SHIFT) & MASK) - ZERO);
int A = (int) (((type >> A_SHIFT) & MASK) - ZERO);
int mol = (int) (((type >> mol_SHIFT) & MASK) - ZERO);
int cd = (int) (((type >> cd_SHIFT) & MASK) - ZERO);
int rad = (int) (((type >> rad_SHIFT) & MASK) - ZERO);
int x = (int) ((type >> x_SHIFT) & MASK);
StringBuffer numerator = new StringBuffer();
StringBuffer denominator = new StringBuffer();
addSIname(m, "m", numerator, denominator);
addSIname(s, "s", numerator, denominator);
addSIname(kg, "kg", numerator, denominator);
addSIname(K, "K", numerator, denominator);
addSIname(A, "A", numerator, denominator);
addSIname(mol, "mol", numerator, denominator);
addSIname(cd, "cd", numerator, denominator);
addSIname(rad, "rad", numerator, denominator);
if (denominator.length() > 0)
{
if (numerator.length() == 0)
{
numerator.append("1");
}
numerator.append("/");
numerator.append((Object)denominator); /* we use (Object) to avoid using new 1.4 method append(StringBuffer) */
}
name = numerator.toString();
}
return name;
}
private void addSIname(int si, String name, StringBuffer numerator, StringBuffer denominator)
{
if (si != 0)
{
StringBuffer sb = (si > 0) ? numerator : denominator;
if (sb.length() > 0)
{
sb.append("*");
}
sb.append(name);
int power = Math.abs(si);
if (power > 1)
{
sb.append("^");
sb.append(power);
}
}
}
/**
* Checks whether the unit has a special type, i.e. not a SI unit.
*
* @return true if the type is special, otherwise false.
*/
private boolean isSpecial()
{
return (type & x_MASK) != 0;
}
}