| 1 | /* |
| 2 | * JScience - Java(TM) Tools and Libraries for the Advancement of Sciences. |
| 3 | * Copyright (C) 2006 - JScience (http://jscience.org/) |
| 4 | * All rights reserved. |
| 5 | * |
| 6 | * Permission to use, copy, modify, and distribute this software is |
| 7 | * freely granted, provided that this notice is preserved. |
| 8 | */ |
| 9 | package javax.measure.unit; |
| 10 | |
| 11 | import java.io.Serializable; |
| 12 | |
| 13 | import javax.measure.converter.ConversionException; |
| 14 | import javax.measure.converter.UnitConverter; |
| 15 | import javax.measure.quantity.Quantity; |
| 16 | |
| 17 | /** |
| 18 | * <p> This class represents units formed by the product of rational powers of |
| 19 | * existing units.</p> |
| 20 | * |
| 21 | * <p> This class maintains the canonical form of this product (simplest |
| 22 | * form after factorization). For example: |
| 23 | * <code>METER.pow(2).divide(METER)</code> returns |
| 24 | * <code>METER</code>.</p> |
| 25 | * |
| 26 | * @author <a href="mailto:jean-marie@dautelle.com">Jean-Marie Dautelle</a> |
| 27 | * @version 3.1, April 22, 2006 |
| 28 | * @see Unit#times(Unit) |
| 29 | * @see Unit#divide(Unit) |
| 30 | * @see Unit#pow(int) |
| 31 | * @see Unit#root(int) |
| 32 | */ |
| 33 | public final class ProductUnit<Q extends Quantity> extends DerivedUnit<Q> { |
| 34 | |
| 35 | /** |
| 36 | * Holds the units composing this product unit. |
| 37 | */ |
| 38 | private final Element[] _elements; |
| 39 | |
| 40 | /** |
| 41 | * Holds the hashcode (optimization). |
| 42 | */ |
| 43 | private int _hashCode; |
| 44 | |
| 45 | /** |
| 46 | * Default constructor (used solely to create <code>ONE</code> instance). |
| 47 | */ |
| 48 | ProductUnit() { |
| 49 | _elements = new Element[0]; |
| 50 | } |
| 51 | |
| 52 | /** |
| 53 | * Copy constructor (allows for parameterization of product units). |
| 54 | * |
| 55 | * @param productUnit the product unit source. |
| 56 | * @throws ClassCastException if the specified unit is not |
| 57 | * a product unit. |
| 58 | */ |
| 59 | public ProductUnit(Unit<?> productUnit) { |
| 60 | _elements = ((ProductUnit<?>)productUnit)._elements; |
| 61 | } |
| 62 | |
| 63 | /** |
| 64 | * Product unit constructor. |
| 65 | * |
| 66 | * @param elements the product elements. |
| 67 | */ |
| 68 | private ProductUnit(Element[] elements) { |
| 69 | _elements = elements; |
| 70 | } |
| 71 | |
| 72 | /** |
| 73 | * Returns the unit defined from the product of the specifed elements. |
| 74 | * |
| 75 | * @param leftElems left multiplicand elements. |
| 76 | * @param rightElems right multiplicand elements. |
| 77 | * @return the corresponding unit. |
| 78 | */ |
| 79 | @SuppressWarnings("unchecked") |
| 80 | private static Unit<? extends Quantity> getInstance(Element[] leftElems, |
| 81 | Element[] rightElems) { |
| 82 | |
| 83 | // Merges left elements with right elements. |
| 84 | Element[] result = new Element[leftElems.length + rightElems.length]; |
| 85 | int resultIndex = 0; |
| 86 | for (int i = 0; i < leftElems.length; i++) { |
| 87 | Unit unit = leftElems[i]._unit; |
| 88 | int p1 = leftElems[i]._pow; |
| 89 | int r1 = leftElems[i]._root; |
| 90 | int p2 = 0; |
| 91 | int r2 = 1; |
| 92 | for (int j = 0; j < rightElems.length; j++) { |
| 93 | if (unit.equals(rightElems[j]._unit)) { |
| 94 | p2 = rightElems[j]._pow; |
| 95 | r2 = rightElems[j]._root; |
| 96 | break; // No duplicate. |
| 97 | } |
| 98 | } |
| 99 | int pow = (p1 * r2) + (p2 * r1); |
| 100 | int root = r1 * r2; |
| 101 | if (pow != 0) { |
| 102 | int gcd = gcd(Math.abs(pow), root); |
| 103 | result[resultIndex++] = new Element(unit, pow / gcd, root / gcd); |
| 104 | } |
| 105 | } |
| 106 | |
| 107 | // Appends remaining right elements not merged. |
| 108 | for (int i = 0; i < rightElems.length; i++) { |
| 109 | Unit unit = rightElems[i]._unit; |
| 110 | boolean hasBeenMerged = false; |
| 111 | for (int j = 0; j < leftElems.length; j++) { |
| 112 | if (unit.equals(leftElems[j]._unit)) { |
| 113 | hasBeenMerged = true; |
| 114 | break; |
| 115 | } |
| 116 | } |
| 117 | if (!hasBeenMerged) { |
| 118 | result[resultIndex++] = rightElems[i]; |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | // Returns or creates instance. |
| 123 | if (resultIndex == 0) { |
| 124 | return ONE; |
| 125 | } else if ((resultIndex == 1) && (result[0]._pow == result[0]._root)) { |
| 126 | return result[0]._unit; |
| 127 | } else { |
| 128 | Element[] elems = new Element[resultIndex]; |
| 129 | for (int i = 0; i < resultIndex; i++) { |
| 130 | elems[i] = result[i]; |
| 131 | } |
| 132 | return new ProductUnit<Quantity>(elems); |
| 133 | } |
| 134 | } |
| 135 | |
| 136 | /** |
| 137 | * Returns the product of the specified units. |
| 138 | * |
| 139 | * @param left the left unit operand. |
| 140 | * @param right the right unit operand. |
| 141 | * @return <code>left * right</code> |
| 142 | */ |
| 143 | static Unit<? extends Quantity> getProductInstance(Unit<?> left, Unit<?> right) { |
| 144 | Element[] leftElems; |
| 145 | if (left instanceof ProductUnit) { |
| 146 | leftElems = ((ProductUnit<?>) left)._elements; |
| 147 | } else { |
| 148 | leftElems = new Element[] { new Element(left, 1, 1) }; |
| 149 | } |
| 150 | Element[] rightElems; |
| 151 | if (right instanceof ProductUnit) { |
| 152 | rightElems = ((ProductUnit<?>) right)._elements; |
| 153 | } else { |
| 154 | rightElems = new Element[] { new Element(right, 1, 1) }; |
| 155 | } |
| 156 | return getInstance(leftElems, rightElems); |
| 157 | } |
| 158 | |
| 159 | /** |
| 160 | * Returns the quotient of the specified units. |
| 161 | * |
| 162 | * @param left the dividend unit operand. |
| 163 | * @param right the divisor unit operand. |
| 164 | * @return <code>dividend / divisor</code> |
| 165 | */ |
| 166 | static Unit<? extends Quantity> getQuotientInstance(Unit<?> left, Unit<?> right) { |
| 167 | Element[] leftElems; |
| 168 | if (left instanceof ProductUnit) { |
| 169 | leftElems = ((ProductUnit<?>) left)._elements; |
| 170 | } else { |
| 171 | leftElems = new Element[] { new Element(left, 1, 1) }; |
| 172 | } |
| 173 | Element[] rightElems; |
| 174 | if (right instanceof ProductUnit) { |
| 175 | Element[] elems = ((ProductUnit<?>) right)._elements; |
| 176 | rightElems = new Element[elems.length]; |
| 177 | for (int i = 0; i < elems.length; i++) { |
| 178 | rightElems[i] = new Element(elems[i]._unit, -elems[i]._pow, |
| 179 | elems[i]._root); |
| 180 | } |
| 181 | } else { |
| 182 | rightElems = new Element[] { new Element(right, -1, 1) }; |
| 183 | } |
| 184 | return getInstance(leftElems, rightElems); |
| 185 | } |
| 186 | |
| 187 | /** |
| 188 | * Returns the product unit corresponding to the specified root of |
| 189 | * the specified unit. |
| 190 | * |
| 191 | * @param unit the unit. |
| 192 | * @param n the root's order (n > 0). |
| 193 | * @return <code>unit^(1/nn)</code> |
| 194 | * @throws ArithmeticException if <code>n == 0</code>. |
| 195 | */ |
| 196 | static Unit<? extends Quantity> getRootInstance(Unit<?> unit, int n) { |
| 197 | Element[] unitElems; |
| 198 | if (unit instanceof ProductUnit) { |
| 199 | Element[] elems = ((ProductUnit<?>) unit)._elements; |
| 200 | unitElems = new Element[elems.length]; |
| 201 | for (int i = 0; i < elems.length; i++) { |
| 202 | int gcd = gcd(Math.abs(elems[i]._pow), elems[i]._root * n); |
| 203 | unitElems[i] = new Element(elems[i]._unit, elems[i]._pow / gcd, |
| 204 | elems[i]._root * n / gcd); |
| 205 | } |
| 206 | } else { |
| 207 | unitElems = new Element[] { new Element(unit, 1, n) }; |
| 208 | } |
| 209 | return getInstance(unitElems, new Element[0]); |
| 210 | } |
| 211 | |
| 212 | /** |
| 213 | * Returns the product unit corresponding to this unit raised to |
| 214 | * the specified exponent. |
| 215 | * |
| 216 | * @param unit the unit. |
| 217 | * @param nn the exponent (nn > 0). |
| 218 | * @return <code>unit^n</code> |
| 219 | */ |
| 220 | static Unit<? extends Quantity> getPowInstance(Unit<?> unit, int n) { |
| 221 | Element[] unitElems; |
| 222 | if (unit instanceof ProductUnit) { |
| 223 | Element[] elems = ((ProductUnit<?>) unit)._elements; |
| 224 | unitElems = new Element[elems.length]; |
| 225 | for (int i = 0; i < elems.length; i++) { |
| 226 | int gcd = gcd(Math.abs(elems[i]._pow * n), elems[i]._root); |
| 227 | unitElems[i] = new Element(elems[i]._unit, elems[i]._pow * n |
| 228 | / gcd, elems[i]._root / gcd); |
| 229 | } |
| 230 | } else { |
| 231 | unitElems = new Element[] { new Element(unit, n, 1) }; |
| 232 | } |
| 233 | return getInstance(unitElems, new Element[0]); |
| 234 | } |
| 235 | |
| 236 | /** |
| 237 | * Returns the number of units in this product. |
| 238 | * |
| 239 | * @return the number of units being multiplied. |
| 240 | */ |
| 241 | public int getUnitCount() { |
| 242 | return _elements.length; |
| 243 | } |
| 244 | |
| 245 | /** |
| 246 | * Returns the unit at the specified position. |
| 247 | * |
| 248 | * @param index the index of the unit to return. |
| 249 | * @return the unit at the specified position. |
| 250 | * @throws IndexOutOfBoundsException if index is out of range |
| 251 | * <code>(index < 0 || index >= size())</code>. |
| 252 | */ |
| 253 | @SuppressWarnings("unchecked") |
| 254 | public Unit<? extends Quantity> getUnit(int index) { |
| 255 | return _elements[index].getUnit(); |
| 256 | } |
| 257 | |
| 258 | /** |
| 259 | * Returns the power exponent of the unit at the specified position. |
| 260 | * |
| 261 | * @param index the index of the unit to return. |
| 262 | * @return the unit power exponent at the specified position. |
| 263 | * @throws IndexOutOfBoundsException if index is out of range |
| 264 | * <code>(index < 0 || index >= size())</code>. |
| 265 | */ |
| 266 | public int getUnitPow(int index) { |
| 267 | return _elements[index].getPow(); |
| 268 | } |
| 269 | |
| 270 | /** |
| 271 | * Returns the root exponent of the unit at the specified position. |
| 272 | * |
| 273 | * @param index the index of the unit to return. |
| 274 | * @return the unit root exponent at the specified position. |
| 275 | * @throws IndexOutOfBoundsException if index is out of range |
| 276 | * <code>(index < 0 || index >= size())</code>. |
| 277 | */ |
| 278 | public int getUnitRoot(int index) { |
| 279 | return _elements[index].getRoot(); |
| 280 | } |
| 281 | |
| 282 | /** |
| 283 | * Indicates if this product unit is considered equals to the specified |
| 284 | * object. |
| 285 | * |
| 286 | * @param that the object to compare for equality. |
| 287 | * @return <code>true</code> if <code>this</code> and <code>that</code> |
| 288 | * are considered equals; <code>false</code>otherwise. |
| 289 | */ |
| 290 | public boolean equals(Object that) { |
| 291 | if (this == that) |
| 292 | return true; |
| 293 | if (that instanceof ProductUnit) { |
| 294 | // Two products are equals if they have the same elements |
| 295 | // regardless of the elements' order. |
| 296 | Element[] elems = ((ProductUnit<?>) that)._elements; |
| 297 | if (_elements.length == elems.length) { |
| 298 | for (int i = 0; i < _elements.length; i++) { |
| 299 | boolean unitFound = false; |
| 300 | for (int j = 0; j < elems.length; j++) { |
| 301 | if (_elements[i]._unit.equals(elems[j]._unit)) { |
| 302 | if ((_elements[i]._pow != elems[j]._pow) |
| 303 | || (_elements[i]._root != elems[j]._root)) { |
| 304 | return false; |
| 305 | } else { |
| 306 | unitFound = true; |
| 307 | break; |
| 308 | } |
| 309 | } |
| 310 | } |
| 311 | if (!unitFound) { |
| 312 | return false; |
| 313 | } |
| 314 | } |
| 315 | return true; |
| 316 | } |
| 317 | } |
| 318 | return false; |
| 319 | } |
| 320 | |
| 321 | @Override |
| 322 | // Implements abstract method. |
| 323 | public int hashCode() { |
| 324 | if (_hashCode != 0) |
| 325 | return _hashCode; |
| 326 | int code = 0; |
| 327 | for (int i = 0; i < _elements.length; i++) { |
| 328 | code += _elements[i]._unit.hashCode() |
| 329 | * (_elements[i]._pow * 3 - _elements[i]._root * 2); |
| 330 | } |
| 331 | _hashCode = code; |
| 332 | return code; |
| 333 | } |
| 334 | |
| 335 | @Override |
| 336 | @SuppressWarnings("unchecked") |
| 337 | public Unit<? super Q> getStandardUnit() { |
| 338 | if (hasOnlyStandardUnit()) |
| 339 | return this; |
| 340 | Unit systemUnit = ONE; |
| 341 | for (int i = 0; i < _elements.length; i++) { |
| 342 | Unit unit = _elements[i]._unit.getStandardUnit(); |
| 343 | unit = unit.pow(_elements[i]._pow); |
| 344 | unit = unit.root(_elements[i]._root); |
| 345 | systemUnit = systemUnit.times(unit); |
| 346 | } |
| 347 | return systemUnit; |
| 348 | } |
| 349 | |
| 350 | @Override |
| 351 | public UnitConverter toStandardUnit() { |
| 352 | if (hasOnlyStandardUnit()) |
| 353 | return UnitConverter.IDENTITY; |
| 354 | UnitConverter converter = UnitConverter.IDENTITY; |
| 355 | for (int i = 0; i < _elements.length; i++) { |
| 356 | UnitConverter cvtr = _elements[i]._unit.toStandardUnit(); |
| 357 | if (!cvtr.isLinear()) |
| 358 | throw new ConversionException(_elements[i]._unit |
| 359 | + " is non-linear, cannot convert"); |
| 360 | if (_elements[i]._root != 1) |
| 361 | throw new ConversionException(_elements[i]._unit |
| 362 | + " holds a base unit with fractional exponent"); |
| 363 | int pow = _elements[i]._pow; |
| 364 | if (pow < 0) { // Negative power. |
| 365 | pow = -pow; |
| 366 | cvtr = cvtr.inverse(); |
| 367 | } |
| 368 | for (int j = 0; j < pow; j++) { |
| 369 | converter = converter.concatenate(cvtr); |
| 370 | } |
| 371 | } |
| 372 | return converter; |
| 373 | } |
| 374 | |
| 375 | /** |
| 376 | * Indicates if this product unit is a standard unit. |
| 377 | * |
| 378 | * @return <code>true</code> if all elements are standard units; |
| 379 | * <code>false</code> otherwise. |
| 380 | */ |
| 381 | private boolean hasOnlyStandardUnit() { |
| 382 | for (int i = 0; i < _elements.length; i++) { |
| 383 | Unit<?> u = _elements[i]._unit; |
| 384 | if (!u.isStandardUnit()) |
| 385 | return false; |
| 386 | } |
| 387 | return true; |
| 388 | } |
| 389 | |
| 390 | /** |
| 391 | * Returns the greatest common divisor (Euclid's algorithm). |
| 392 | * |
| 393 | * @param m the first number. |
| 394 | * @param nn the second number. |
| 395 | * @return the greatest common divisor. |
| 396 | */ |
| 397 | private static int gcd(int m, int n) { |
| 398 | if (n == 0) { |
| 399 | return m; |
| 400 | } else { |
| 401 | return gcd(n, m % n); |
| 402 | } |
| 403 | } |
| 404 | |
| 405 | /** |
| 406 | * Inner product element represents a rational power of a single unit. |
| 407 | */ |
| 408 | private final static class Element implements Serializable { |
| 409 | |
| 410 | /** |
| 411 | * Holds the single unit. |
| 412 | */ |
| 413 | private final Unit<?> _unit; |
| 414 | |
| 415 | /** |
| 416 | * Holds the power exponent. |
| 417 | */ |
| 418 | private final int _pow; |
| 419 | |
| 420 | /** |
| 421 | * Holds the root exponent. |
| 422 | */ |
| 423 | private final int _root; |
| 424 | |
| 425 | /** |
| 426 | * Structural constructor. |
| 427 | * |
| 428 | * @param unit the unit. |
| 429 | * @param pow the power exponent. |
| 430 | * @param root the root exponent. |
| 431 | */ |
| 432 | private Element(Unit<?> unit, int pow, int root) { |
| 433 | _unit = unit; |
| 434 | _pow = pow; |
| 435 | _root = root; |
| 436 | } |
| 437 | |
| 438 | /** |
| 439 | * Returns this element's unit. |
| 440 | * |
| 441 | * @return the single unit. |
| 442 | */ |
| 443 | public Unit<?> getUnit() { |
| 444 | return _unit; |
| 445 | } |
| 446 | |
| 447 | /** |
| 448 | * Returns the power exponent. The power exponent can be negative |
| 449 | * but is always different from zero. |
| 450 | * |
| 451 | * @return the power exponent of the single unit. |
| 452 | */ |
| 453 | public int getPow() { |
| 454 | return _pow; |
| 455 | } |
| 456 | |
| 457 | /** |
| 458 | * Returns the root exponent. The root exponent is always greater |
| 459 | * than zero. |
| 460 | * |
| 461 | * @return the root exponent of the single unit. |
| 462 | */ |
| 463 | public int getRoot() { |
| 464 | return _root; |
| 465 | } |
| 466 | |
| 467 | private static final long serialVersionUID = 1L; |
| 468 | } |
| 469 | |
| 470 | private static final long serialVersionUID = 1L; |
| 471 | } |