| /* |
| * JScience - Java(TM) Tools and Libraries for the Advancement of Sciences. |
| * Copyright (C) 2006 - JScience (http://jscience.org/) |
| * All rights reserved. |
| * |
| * Permission to use, copy, modify, and distribute this software is |
| * freely granted, provided that this notice is preserved. |
| */ |
| package javax.measure.unit; |
| |
| import java.io.Serializable; |
| |
| import javax.measure.converter.ConversionException; |
| import javax.measure.converter.UnitConverter; |
| import javax.measure.quantity.Quantity; |
| |
| /** |
| * <p> This class represents units formed by the product of rational powers of |
| * existing units.</p> |
| * |
| * <p> This class maintains the canonical form of this product (simplest |
| * form after factorization). For example: |
| * <code>METER.pow(2).divide(METER)</code> returns |
| * <code>METER</code>.</p> |
| * |
| * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a> |
| * @version 3.1, April 22, 2006 |
| * @see Unit#times(Unit) |
| * @see Unit#divide(Unit) |
| * @see Unit#pow(int) |
| * @see Unit#root(int) |
| */ |
| public final class ProductUnit<Q extends Quantity> extends DerivedUnit<Q> { |
| |
| /** |
| * Holds the units composing this product unit. |
| */ |
| private final Element[] _elements; |
| |
| /** |
| * Holds the hashcode (optimization). |
| */ |
| private int _hashCode; |
| |
| /** |
| * Default constructor (used solely to create <code>ONE</code> instance). |
| */ |
| ProductUnit() { |
| _elements = new Element[0]; |
| } |
| |
| /** |
| * Copy constructor (allows for parameterization of product units). |
| * |
| * @param productUnit the product unit source. |
| * @throws ClassCastException if the specified unit is not |
| * a product unit. |
| */ |
| public ProductUnit(Unit<?> productUnit) { |
| _elements = ((ProductUnit<?>)productUnit)._elements; |
| } |
| |
| /** |
| * Product unit constructor. |
| * |
| * @param elements the product elements. |
| */ |
| private ProductUnit(Element[] elements) { |
| _elements = elements; |
| } |
| |
| /** |
| * Returns the unit defined from the product of the specifed elements. |
| * |
| * @param leftElems left multiplicand elements. |
| * @param rightElems right multiplicand elements. |
| * @return the corresponding unit. |
| */ |
| @SuppressWarnings("rawtypes") |
| private static Unit<? extends Quantity> getInstance(Element[] leftElems, |
| Element[] rightElems) { |
| |
| // Merges left elements with right elements. |
| Element[] result = new Element[leftElems.length + rightElems.length]; |
| int resultIndex = 0; |
| for (int i = 0; i < leftElems.length; i++) { |
| Unit unit = leftElems[i]._unit; |
| int p1 = leftElems[i]._pow; |
| int r1 = leftElems[i]._root; |
| int p2 = 0; |
| int r2 = 1; |
| for (int j = 0; j < rightElems.length; j++) { |
| if (unit.equals(rightElems[j]._unit)) { |
| p2 = rightElems[j]._pow; |
| r2 = rightElems[j]._root; |
| break; // No duplicate. |
| } |
| } |
| int pow = (p1 * r2) + (p2 * r1); |
| int root = r1 * r2; |
| if (pow != 0) { |
| int gcd = gcd(Math.abs(pow), root); |
| result[resultIndex++] = new Element(unit, pow / gcd, root / gcd); |
| } |
| } |
| |
| // Appends remaining right elements not merged. |
| for (int i = 0; i < rightElems.length; i++) { |
| Unit unit = rightElems[i]._unit; |
| boolean hasBeenMerged = false; |
| for (int j = 0; j < leftElems.length; j++) { |
| if (unit.equals(leftElems[j]._unit)) { |
| hasBeenMerged = true; |
| break; |
| } |
| } |
| if (!hasBeenMerged) { |
| result[resultIndex++] = rightElems[i]; |
| } |
| } |
| |
| // Returns or creates instance. |
| if (resultIndex == 0) { |
| return ONE; |
| } else if ((resultIndex == 1) && (result[0]._pow == result[0]._root)) { |
| return result[0]._unit; |
| } else { |
| Element[] elems = new Element[resultIndex]; |
| for (int i = 0; i < resultIndex; i++) { |
| elems[i] = result[i]; |
| } |
| return new ProductUnit<Quantity>(elems); |
| } |
| } |
| |
| /** |
| * Returns the product of the specified units. |
| * |
| * @param left the left unit operand. |
| * @param right the right unit operand. |
| * @return <code>left * right</code> |
| */ |
| static Unit<? extends Quantity> getProductInstance(Unit<?> left, Unit<?> right) { |
| Element[] leftElems; |
| if (left instanceof ProductUnit) { |
| leftElems = ((ProductUnit<?>) left)._elements; |
| } else { |
| leftElems = new Element[] { new Element(left, 1, 1) }; |
| } |
| Element[] rightElems; |
| if (right instanceof ProductUnit) { |
| rightElems = ((ProductUnit<?>) right)._elements; |
| } else { |
| rightElems = new Element[] { new Element(right, 1, 1) }; |
| } |
| return getInstance(leftElems, rightElems); |
| } |
| |
| /** |
| * Returns the quotient of the specified units. |
| * |
| * @param left the dividend unit operand. |
| * @param right the divisor unit operand. |
| * @return <code>dividend / divisor</code> |
| */ |
| static Unit<? extends Quantity> getQuotientInstance(Unit<?> left, Unit<?> right) { |
| Element[] leftElems; |
| if (left instanceof ProductUnit) { |
| leftElems = ((ProductUnit<?>) left)._elements; |
| } else { |
| leftElems = new Element[] { new Element(left, 1, 1) }; |
| } |
| Element[] rightElems; |
| if (right instanceof ProductUnit) { |
| Element[] elems = ((ProductUnit<?>) right)._elements; |
| rightElems = new Element[elems.length]; |
| for (int i = 0; i < elems.length; i++) { |
| rightElems[i] = new Element(elems[i]._unit, -elems[i]._pow, |
| elems[i]._root); |
| } |
| } else { |
| rightElems = new Element[] { new Element(right, -1, 1) }; |
| } |
| return getInstance(leftElems, rightElems); |
| } |
| |
| /** |
| * Returns the product unit corresponding to the specified root of |
| * the specified unit. |
| * |
| * @param unit the unit. |
| * @param n the root's order (n > 0). |
| * @return <code>unit^(1/nn)</code> |
| * @throws ArithmeticException if <code>n == 0</code>. |
| */ |
| static Unit<? extends Quantity> getRootInstance(Unit<?> unit, int n) { |
| Element[] unitElems; |
| if (unit instanceof ProductUnit) { |
| Element[] elems = ((ProductUnit<?>) unit)._elements; |
| unitElems = new Element[elems.length]; |
| for (int i = 0; i < elems.length; i++) { |
| int gcd = gcd(Math.abs(elems[i]._pow), elems[i]._root * n); |
| unitElems[i] = new Element(elems[i]._unit, elems[i]._pow / gcd, |
| elems[i]._root * n / gcd); |
| } |
| } else { |
| unitElems = new Element[] { new Element(unit, 1, n) }; |
| } |
| return getInstance(unitElems, new Element[0]); |
| } |
| |
| /** |
| * Returns the product unit corresponding to this unit raised to |
| * the specified exponent. |
| * |
| * @param unit the unit. |
| * @param nn the exponent (nn > 0). |
| * @return <code>unit^n</code> |
| */ |
| static Unit<? extends Quantity> getPowInstance(Unit<?> unit, int n) { |
| Element[] unitElems; |
| if (unit instanceof ProductUnit) { |
| Element[] elems = ((ProductUnit<?>) unit)._elements; |
| unitElems = new Element[elems.length]; |
| for (int i = 0; i < elems.length; i++) { |
| int gcd = gcd(Math.abs(elems[i]._pow * n), elems[i]._root); |
| unitElems[i] = new Element(elems[i]._unit, elems[i]._pow * n |
| / gcd, elems[i]._root / gcd); |
| } |
| } else { |
| unitElems = new Element[] { new Element(unit, n, 1) }; |
| } |
| return getInstance(unitElems, new Element[0]); |
| } |
| |
| /** |
| * Returns the number of units in this product. |
| * |
| * @return the number of units being multiplied. |
| */ |
| public int getUnitCount() { |
| return _elements.length; |
| } |
| |
| /** |
| * Returns the unit at the specified position. |
| * |
| * @param index the index of the unit to return. |
| * @return the unit at the specified position. |
| * @throws IndexOutOfBoundsException if index is out of range |
| * <code>(index < 0 || index >= size())</code>. |
| */ |
| public Unit<? extends Quantity> getUnit(int index) { |
| return _elements[index].getUnit(); |
| } |
| |
| /** |
| * Returns the power exponent of the unit at the specified position. |
| * |
| * @param index the index of the unit to return. |
| * @return the unit power exponent at the specified position. |
| * @throws IndexOutOfBoundsException if index is out of range |
| * <code>(index < 0 || index >= size())</code>. |
| */ |
| public int getUnitPow(int index) { |
| return _elements[index].getPow(); |
| } |
| |
| /** |
| * Returns the root exponent of the unit at the specified position. |
| * |
| * @param index the index of the unit to return. |
| * @return the unit root exponent at the specified position. |
| * @throws IndexOutOfBoundsException if index is out of range |
| * <code>(index < 0 || index >= size())</code>. |
| */ |
| public int getUnitRoot(int index) { |
| return _elements[index].getRoot(); |
| } |
| |
| /** |
| * Indicates if this product unit is considered equals to the specified |
| * object. |
| * |
| * @param that the object to compare for equality. |
| * @return <code>true</code> if <code>this</code> and <code>that</code> |
| * are considered equals; <code>false</code>otherwise. |
| */ |
| public boolean equals(Object that) { |
| if (this == that) |
| return true; |
| if (that instanceof ProductUnit) { |
| // Two products are equals if they have the same elements |
| // regardless of the elements' order. |
| Element[] elems = ((ProductUnit<?>) that)._elements; |
| if (_elements.length == elems.length) { |
| for (int i = 0; i < _elements.length; i++) { |
| boolean unitFound = false; |
| for (int j = 0; j < elems.length; j++) { |
| if (_elements[i]._unit.equals(elems[j]._unit)) { |
| if ((_elements[i]._pow != elems[j]._pow) |
| || (_elements[i]._root != elems[j]._root)) { |
| return false; |
| } else { |
| unitFound = true; |
| break; |
| } |
| } |
| } |
| if (!unitFound) { |
| return false; |
| } |
| } |
| return true; |
| } |
| } |
| return false; |
| } |
| |
| @Override |
| // Implements abstract method. |
| public int hashCode() { |
| if (_hashCode != 0) |
| return _hashCode; |
| int code = 0; |
| for (int i = 0; i < _elements.length; i++) { |
| code += _elements[i]._unit.hashCode() |
| * (_elements[i]._pow * 3 - _elements[i]._root * 2); |
| } |
| _hashCode = code; |
| return code; |
| } |
| |
| @Override |
| @SuppressWarnings({ "unchecked", "rawtypes" }) |
| public Unit<? super Q> getStandardUnit() { |
| if (hasOnlyStandardUnit()) |
| return this; |
| Unit systemUnit = ONE; |
| for (int i = 0; i < _elements.length; i++) { |
| Unit unit = _elements[i]._unit.getStandardUnit(); |
| unit = unit.pow(_elements[i]._pow); |
| unit = unit.root(_elements[i]._root); |
| systemUnit = systemUnit.times(unit); |
| } |
| return systemUnit; |
| } |
| |
| @Override |
| public UnitConverter toStandardUnit() { |
| if (hasOnlyStandardUnit()) |
| return UnitConverter.IDENTITY; |
| UnitConverter converter = UnitConverter.IDENTITY; |
| for (int i = 0; i < _elements.length; i++) { |
| UnitConverter cvtr = _elements[i]._unit.toStandardUnit(); |
| if (!cvtr.isLinear()) |
| throw new ConversionException(_elements[i]._unit |
| + " is non-linear, cannot convert"); |
| if (_elements[i]._root != 1) |
| throw new ConversionException(_elements[i]._unit |
| + " holds a base unit with fractional exponent"); |
| int pow = _elements[i]._pow; |
| if (pow < 0) { // Negative power. |
| pow = -pow; |
| cvtr = cvtr.inverse(); |
| } |
| for (int j = 0; j < pow; j++) { |
| converter = converter.concatenate(cvtr); |
| } |
| } |
| return converter; |
| } |
| |
| /** |
| * Indicates if this product unit is a standard unit. |
| * |
| * @return <code>true</code> if all elements are standard units; |
| * <code>false</code> otherwise. |
| */ |
| private boolean hasOnlyStandardUnit() { |
| for (int i = 0; i < _elements.length; i++) { |
| Unit<?> u = _elements[i]._unit; |
| if (!u.isStandardUnit()) |
| return false; |
| } |
| return true; |
| } |
| |
| /** |
| * Returns the greatest common divisor (Euclid's algorithm). |
| * |
| * @param m the first number. |
| * @param nn the second number. |
| * @return the greatest common divisor. |
| */ |
| private static int gcd(int m, int n) { |
| if (n == 0) { |
| return m; |
| } else { |
| return gcd(n, m % n); |
| } |
| } |
| |
| /** |
| * Inner product element represents a rational power of a single unit. |
| */ |
| private final static class Element implements Serializable { |
| |
| /** |
| * Holds the single unit. |
| */ |
| private final Unit<?> _unit; |
| |
| /** |
| * Holds the power exponent. |
| */ |
| private final int _pow; |
| |
| /** |
| * Holds the root exponent. |
| */ |
| private final int _root; |
| |
| /** |
| * Structural constructor. |
| * |
| * @param unit the unit. |
| * @param pow the power exponent. |
| * @param root the root exponent. |
| */ |
| private Element(Unit<?> unit, int pow, int root) { |
| _unit = unit; |
| _pow = pow; |
| _root = root; |
| } |
| |
| /** |
| * Returns this element's unit. |
| * |
| * @return the single unit. |
| */ |
| public Unit<?> getUnit() { |
| return _unit; |
| } |
| |
| /** |
| * Returns the power exponent. The power exponent can be negative |
| * but is always different from zero. |
| * |
| * @return the power exponent of the single unit. |
| */ |
| public int getPow() { |
| return _pow; |
| } |
| |
| /** |
| * Returns the root exponent. The root exponent is always greater |
| * than zero. |
| * |
| * @return the root exponent of the single unit. |
| */ |
| public int getRoot() { |
| return _root; |
| } |
| |
| private static final long serialVersionUID = 1L; |
| } |
| |
| private static final long serialVersionUID = 1L; |
| } |