1 /* 2 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. Oracle designates this 7 * particular file as subject to the "Classpath" exception as provided 8 * by Oracle in the LICENSE file that accompanied this code. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 */ 24 25 /* 26 * This file is available under and governed by the GNU General Public 27 * License version 2 only, as published by the Free Software Foundation. 28 * However, the following notice accompanied the original version of this 29 * file: 30 * 31 * Written by Doug Lea with assistance from members of JCP JSR-166 32 * Expert Group and released to the public domain, as explained at 33 * http://creativecommons.org/publicdomain/zero/1.0/ 34 */ 35 36 package java.util.concurrent; 37 38 import java.io.ObjectStreamField; 39 import java.util.Random; 40 import java.util.Spliterator; 41 import java.util.concurrent.atomic.AtomicInteger; 42 import java.util.concurrent.atomic.AtomicLong; 43 import java.util.function.DoubleConsumer; 44 import java.util.function.IntConsumer; 45 import java.util.function.LongConsumer; 46 import java.util.stream.DoubleStream; 47 import java.util.stream.IntStream; 48 import java.util.stream.LongStream; 49 import java.util.stream.StreamSupport; 50 51 /** 52 * A random number generator isolated to the current thread. Like the 53 * global {@link java.util.Random} generator used by the {@link 54 * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized 55 * with an internally generated seed that may not otherwise be 56 * modified. When applicable, use of {@code ThreadLocalRandom} rather 57 * than shared {@code Random} objects in concurrent programs will 58 * typically encounter much less overhead and contention. Use of 59 * {@code ThreadLocalRandom} is particularly appropriate when multiple 60 * tasks (for example, each a {@link ForkJoinTask}) use random numbers 61 * in parallel in thread pools. 62 * 63 * <p>Usages of this class should typically be of the form: 64 * {@code ThreadLocalRandom.current().nextX(...)} (where 65 * {@code X} is {@code Int}, {@code Long}, etc). 66 * When all usages are of this form, it is never possible to 67 * accidently share a {@code ThreadLocalRandom} across multiple threads. 68 * 69 * <p>This class also provides additional commonly used bounded random 70 * generation methods. 71 * 72 * <p>Instances of {@code ThreadLocalRandom} are not cryptographically 73 * secure. Consider instead using {@link java.security.SecureRandom} 74 * in security-sensitive applications. Additionally, 75 * default-constructed instances do not use a cryptographically random 76 * seed unless the {@linkplain System#getProperty system property} 77 * {@code java.util.secureRandomSeed} is set to {@code true}. 78 * 79 * @since 1.7 80 * @author Doug Lea 81 */ 82 public class ThreadLocalRandom extends Random { 83 /* 84 * This class implements the java.util.Random API (and subclasses 85 * Random) using a single static instance that accesses random 86 * number state held in class Thread (primarily, field 87 * threadLocalRandomSeed). In doing so, it also provides a home 88 * for managing package-private utilities that rely on exactly the 89 * same state as needed to maintain the ThreadLocalRandom 90 * instances. We leverage the need for an initialization flag 91 * field to also use it as a "probe" -- a self-adjusting thread 92 * hash used for contention avoidance, as well as a secondary 93 * simpler (xorShift) random seed that is conservatively used to 94 * avoid otherwise surprising users by hijacking the 95 * ThreadLocalRandom sequence. The dual use is a marriage of 96 * convenience, but is a simple and efficient way of reducing 97 * application-level overhead and footprint of most concurrent 98 * programs. 99 * 100 * Even though this class subclasses java.util.Random, it uses the 101 * same basic algorithm as java.util.SplittableRandom. (See its 102 * internal documentation for explanations, which are not repeated 103 * here.) Because ThreadLocalRandoms are not splittable 104 * though, we use only a single 64bit gamma. 105 * 106 * Because this class is in a different package than class Thread, 107 * field access methods use Unsafe to bypass access control rules. 108 * To conform to the requirements of the Random superclass 109 * constructor, the common static ThreadLocalRandom maintains an 110 * "initialized" field for the sake of rejecting user calls to 111 * setSeed while still allowing a call from constructor. Note 112 * that serialization is completely unnecessary because there is 113 * only a static singleton. But we generate a serial form 114 * containing "rnd" and "initialized" fields to ensure 115 * compatibility across versions. 116 * 117 * Implementations of non-core methods are mostly the same as in 118 * SplittableRandom, that were in part derived from a previous 119 * version of this class. 120 * 121 * The nextLocalGaussian ThreadLocal supports the very rarely used 122 * nextGaussian method by providing a holder for the second of a 123 * pair of them. As is true for the base class version of this 124 * method, this time/space tradeoff is probably never worthwhile, 125 * but we provide identical statistical properties. 126 */ 127 mix64(long z)128 private static long mix64(long z) { 129 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; 130 z = (z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L; 131 return z ^ (z >>> 33); 132 } 133 mix32(long z)134 private static int mix32(long z) { 135 z = (z ^ (z >>> 33)) * 0xff51afd7ed558ccdL; 136 return (int)(((z ^ (z >>> 33)) * 0xc4ceb9fe1a85ec53L) >>> 32); 137 } 138 139 /** 140 * Field used only during singleton initialization. 141 * True when constructor completes. 142 */ 143 boolean initialized; 144 145 /** Constructor used only for static singleton */ ThreadLocalRandom()146 private ThreadLocalRandom() { 147 initialized = true; // false during super() call 148 } 149 150 /** 151 * Initialize Thread fields for the current thread. Called only 152 * when Thread.threadLocalRandomProbe is zero, indicating that a 153 * thread local seed value needs to be generated. Note that even 154 * though the initialization is purely thread-local, we need to 155 * rely on (static) atomic generators to initialize the values. 156 */ localInit()157 static final void localInit() { 158 int p = probeGenerator.addAndGet(PROBE_INCREMENT); 159 int probe = (p == 0) ? 1 : p; // skip 0 160 long seed = mix64(seeder.getAndAdd(SEEDER_INCREMENT)); 161 Thread t = Thread.currentThread(); 162 U.putLong(t, SEED, seed); 163 U.putInt(t, PROBE, probe); 164 } 165 166 /** 167 * Returns the current thread's {@code ThreadLocalRandom}. 168 * 169 * @return the current thread's {@code ThreadLocalRandom} 170 */ current()171 public static ThreadLocalRandom current() { 172 if (U.getInt(Thread.currentThread(), PROBE) == 0) 173 localInit(); 174 return instance; 175 } 176 177 /** 178 * Throws {@code UnsupportedOperationException}. Setting seeds in 179 * this generator is not supported. 180 * 181 * @throws UnsupportedOperationException always 182 */ setSeed(long seed)183 public void setSeed(long seed) { 184 // only allow call from super() constructor 185 if (initialized) 186 throw new UnsupportedOperationException(); 187 } 188 nextSeed()189 final long nextSeed() { 190 Thread t; long r; // read and update per-thread seed 191 U.putLong(t = Thread.currentThread(), SEED, 192 r = U.getLong(t, SEED) + GAMMA); 193 return r; 194 } 195 196 // We must define this, but never use it. next(int bits)197 protected int next(int bits) { 198 return (int)(mix64(nextSeed()) >>> (64 - bits)); 199 } 200 201 /** 202 * The form of nextLong used by LongStream Spliterators. If 203 * origin is greater than bound, acts as unbounded form of 204 * nextLong, else as bounded form. 205 * 206 * @param origin the least value, unless greater than bound 207 * @param bound the upper bound (exclusive), must not equal origin 208 * @return a pseudorandom value 209 */ internalNextLong(long origin, long bound)210 final long internalNextLong(long origin, long bound) { 211 long r = mix64(nextSeed()); 212 if (origin < bound) { 213 long n = bound - origin, m = n - 1; 214 if ((n & m) == 0L) // power of two 215 r = (r & m) + origin; 216 else if (n > 0L) { // reject over-represented candidates 217 for (long u = r >>> 1; // ensure nonnegative 218 u + m - (r = u % n) < 0L; // rejection check 219 u = mix64(nextSeed()) >>> 1) // retry 220 ; 221 r += origin; 222 } 223 else { // range not representable as long 224 while (r < origin || r >= bound) 225 r = mix64(nextSeed()); 226 } 227 } 228 return r; 229 } 230 231 /** 232 * The form of nextInt used by IntStream Spliterators. 233 * Exactly the same as long version, except for types. 234 * 235 * @param origin the least value, unless greater than bound 236 * @param bound the upper bound (exclusive), must not equal origin 237 * @return a pseudorandom value 238 */ internalNextInt(int origin, int bound)239 final int internalNextInt(int origin, int bound) { 240 int r = mix32(nextSeed()); 241 if (origin < bound) { 242 int n = bound - origin, m = n - 1; 243 if ((n & m) == 0) 244 r = (r & m) + origin; 245 else if (n > 0) { 246 for (int u = r >>> 1; 247 u + m - (r = u % n) < 0; 248 u = mix32(nextSeed()) >>> 1) 249 ; 250 r += origin; 251 } 252 else { 253 while (r < origin || r >= bound) 254 r = mix32(nextSeed()); 255 } 256 } 257 return r; 258 } 259 260 /** 261 * The form of nextDouble used by DoubleStream Spliterators. 262 * 263 * @param origin the least value, unless greater than bound 264 * @param bound the upper bound (exclusive), must not equal origin 265 * @return a pseudorandom value 266 */ internalNextDouble(double origin, double bound)267 final double internalNextDouble(double origin, double bound) { 268 double r = (nextLong() >>> 11) * DOUBLE_UNIT; 269 if (origin < bound) { 270 r = r * (bound - origin) + origin; 271 if (r >= bound) // correct for rounding 272 r = Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); 273 } 274 return r; 275 } 276 277 /** 278 * Returns a pseudorandom {@code int} value. 279 * 280 * @return a pseudorandom {@code int} value 281 */ nextInt()282 public int nextInt() { 283 return mix32(nextSeed()); 284 } 285 286 /** 287 * Returns a pseudorandom {@code int} value between zero (inclusive) 288 * and the specified bound (exclusive). 289 * 290 * @param bound the upper bound (exclusive). Must be positive. 291 * @return a pseudorandom {@code int} value between zero 292 * (inclusive) and the bound (exclusive) 293 * @throws IllegalArgumentException if {@code bound} is not positive 294 */ nextInt(int bound)295 public int nextInt(int bound) { 296 if (bound <= 0) 297 throw new IllegalArgumentException(BAD_BOUND); 298 int r = mix32(nextSeed()); 299 int m = bound - 1; 300 if ((bound & m) == 0) // power of two 301 r &= m; 302 else { // reject over-represented candidates 303 for (int u = r >>> 1; 304 u + m - (r = u % bound) < 0; 305 u = mix32(nextSeed()) >>> 1) 306 ; 307 } 308 return r; 309 } 310 311 /** 312 * Returns a pseudorandom {@code int} value between the specified 313 * origin (inclusive) and the specified bound (exclusive). 314 * 315 * @param origin the least value returned 316 * @param bound the upper bound (exclusive) 317 * @return a pseudorandom {@code int} value between the origin 318 * (inclusive) and the bound (exclusive) 319 * @throws IllegalArgumentException if {@code origin} is greater than 320 * or equal to {@code bound} 321 */ nextInt(int origin, int bound)322 public int nextInt(int origin, int bound) { 323 if (origin >= bound) 324 throw new IllegalArgumentException(BAD_RANGE); 325 return internalNextInt(origin, bound); 326 } 327 328 /** 329 * Returns a pseudorandom {@code long} value. 330 * 331 * @return a pseudorandom {@code long} value 332 */ nextLong()333 public long nextLong() { 334 return mix64(nextSeed()); 335 } 336 337 /** 338 * Returns a pseudorandom {@code long} value between zero (inclusive) 339 * and the specified bound (exclusive). 340 * 341 * @param bound the upper bound (exclusive). Must be positive. 342 * @return a pseudorandom {@code long} value between zero 343 * (inclusive) and the bound (exclusive) 344 * @throws IllegalArgumentException if {@code bound} is not positive 345 */ nextLong(long bound)346 public long nextLong(long bound) { 347 if (bound <= 0) 348 throw new IllegalArgumentException(BAD_BOUND); 349 long r = mix64(nextSeed()); 350 long m = bound - 1; 351 if ((bound & m) == 0L) // power of two 352 r &= m; 353 else { // reject over-represented candidates 354 for (long u = r >>> 1; 355 u + m - (r = u % bound) < 0L; 356 u = mix64(nextSeed()) >>> 1) 357 ; 358 } 359 return r; 360 } 361 362 /** 363 * Returns a pseudorandom {@code long} value between the specified 364 * origin (inclusive) and the specified bound (exclusive). 365 * 366 * @param origin the least value returned 367 * @param bound the upper bound (exclusive) 368 * @return a pseudorandom {@code long} value between the origin 369 * (inclusive) and the bound (exclusive) 370 * @throws IllegalArgumentException if {@code origin} is greater than 371 * or equal to {@code bound} 372 */ nextLong(long origin, long bound)373 public long nextLong(long origin, long bound) { 374 if (origin >= bound) 375 throw new IllegalArgumentException(BAD_RANGE); 376 return internalNextLong(origin, bound); 377 } 378 379 /** 380 * Returns a pseudorandom {@code double} value between zero 381 * (inclusive) and one (exclusive). 382 * 383 * @return a pseudorandom {@code double} value between zero 384 * (inclusive) and one (exclusive) 385 */ nextDouble()386 public double nextDouble() { 387 return (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT; 388 } 389 390 /** 391 * Returns a pseudorandom {@code double} value between 0.0 392 * (inclusive) and the specified bound (exclusive). 393 * 394 * @param bound the upper bound (exclusive). Must be positive. 395 * @return a pseudorandom {@code double} value between zero 396 * (inclusive) and the bound (exclusive) 397 * @throws IllegalArgumentException if {@code bound} is not positive 398 */ nextDouble(double bound)399 public double nextDouble(double bound) { 400 if (!(bound > 0.0)) 401 throw new IllegalArgumentException(BAD_BOUND); 402 double result = (mix64(nextSeed()) >>> 11) * DOUBLE_UNIT * bound; 403 return (result < bound) ? result : // correct for rounding 404 Double.longBitsToDouble(Double.doubleToLongBits(bound) - 1); 405 } 406 407 /** 408 * Returns a pseudorandom {@code double} value between the specified 409 * origin (inclusive) and bound (exclusive). 410 * 411 * @param origin the least value returned 412 * @param bound the upper bound (exclusive) 413 * @return a pseudorandom {@code double} value between the origin 414 * (inclusive) and the bound (exclusive) 415 * @throws IllegalArgumentException if {@code origin} is greater than 416 * or equal to {@code bound} 417 */ nextDouble(double origin, double bound)418 public double nextDouble(double origin, double bound) { 419 if (!(origin < bound)) 420 throw new IllegalArgumentException(BAD_RANGE); 421 return internalNextDouble(origin, bound); 422 } 423 424 /** 425 * Returns a pseudorandom {@code boolean} value. 426 * 427 * @return a pseudorandom {@code boolean} value 428 */ nextBoolean()429 public boolean nextBoolean() { 430 return mix32(nextSeed()) < 0; 431 } 432 433 /** 434 * Returns a pseudorandom {@code float} value between zero 435 * (inclusive) and one (exclusive). 436 * 437 * @return a pseudorandom {@code float} value between zero 438 * (inclusive) and one (exclusive) 439 */ nextFloat()440 public float nextFloat() { 441 return (mix32(nextSeed()) >>> 8) * FLOAT_UNIT; 442 } 443 nextGaussian()444 public double nextGaussian() { 445 // Use nextLocalGaussian instead of nextGaussian field 446 Double d = nextLocalGaussian.get(); 447 if (d != null) { 448 nextLocalGaussian.set(null); 449 return d.doubleValue(); 450 } 451 double v1, v2, s; 452 do { 453 v1 = 2 * nextDouble() - 1; // between -1 and 1 454 v2 = 2 * nextDouble() - 1; // between -1 and 1 455 s = v1 * v1 + v2 * v2; 456 } while (s >= 1 || s == 0); 457 double multiplier = StrictMath.sqrt(-2 * StrictMath.log(s)/s); 458 nextLocalGaussian.set(new Double(v2 * multiplier)); 459 return v1 * multiplier; 460 } 461 462 // stream methods, coded in a way intended to better isolate for 463 // maintenance purposes the small differences across forms. 464 /** 465 * Returns a stream producing the given {@code streamSize} number of 466 * pseudorandom {@code int} values. 467 * 468 * @param streamSize the number of values to generate 469 * @return a stream of pseudorandom {@code int} values 470 * @throws IllegalArgumentException if {@code streamSize} is 471 * less than zero 472 * @since 1.8 473 */ ints(long streamSize)474 public IntStream ints(long streamSize) { 475 if (streamSize < 0L) 476 throw new IllegalArgumentException(BAD_SIZE); 477 return StreamSupport.intStream 478 (new RandomIntsSpliterator 479 (0L, streamSize, Integer.MAX_VALUE, 0), 480 false); 481 } 482 483 /** 484 * Returns an effectively unlimited stream of pseudorandom {@code int} 485 * values. 486 * 487 * @implNote This method is implemented to be equivalent to {@code 488 * ints(Long.MAX_VALUE)}. 489 * 490 * @return a stream of pseudorandom {@code int} values 491 * @since 1.8 492 */ ints()493 public IntStream ints() { 494 return StreamSupport.intStream 495 (new RandomIntsSpliterator 496 (0L, Long.MAX_VALUE, Integer.MAX_VALUE, 0), 497 false); 498 } 499 500 /** 501 * Returns a stream producing the given {@code streamSize} number 502 * of pseudorandom {@code int} values, each conforming to the given 503 * origin (inclusive) and bound (exclusive). 504 * 505 * @param streamSize the number of values to generate 506 * @param randomNumberOrigin the origin (inclusive) of each random value 507 * @param randomNumberBound the bound (exclusive) of each random value 508 * @return a stream of pseudorandom {@code int} values, 509 * each with the given origin (inclusive) and bound (exclusive) 510 * @throws IllegalArgumentException if {@code streamSize} is 511 * less than zero, or {@code randomNumberOrigin} 512 * is greater than or equal to {@code randomNumberBound} 513 * @since 1.8 514 */ ints(long streamSize, int randomNumberOrigin, int randomNumberBound)515 public IntStream ints(long streamSize, int randomNumberOrigin, 516 int randomNumberBound) { 517 if (streamSize < 0L) 518 throw new IllegalArgumentException(BAD_SIZE); 519 if (randomNumberOrigin >= randomNumberBound) 520 throw new IllegalArgumentException(BAD_RANGE); 521 return StreamSupport.intStream 522 (new RandomIntsSpliterator 523 (0L, streamSize, randomNumberOrigin, randomNumberBound), 524 false); 525 } 526 527 /** 528 * Returns an effectively unlimited stream of pseudorandom {@code 529 * int} values, each conforming to the given origin (inclusive) and bound 530 * (exclusive). 531 * 532 * @implNote This method is implemented to be equivalent to {@code 533 * ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 534 * 535 * @param randomNumberOrigin the origin (inclusive) of each random value 536 * @param randomNumberBound the bound (exclusive) of each random value 537 * @return a stream of pseudorandom {@code int} values, 538 * each with the given origin (inclusive) and bound (exclusive) 539 * @throws IllegalArgumentException if {@code randomNumberOrigin} 540 * is greater than or equal to {@code randomNumberBound} 541 * @since 1.8 542 */ ints(int randomNumberOrigin, int randomNumberBound)543 public IntStream ints(int randomNumberOrigin, int randomNumberBound) { 544 if (randomNumberOrigin >= randomNumberBound) 545 throw new IllegalArgumentException(BAD_RANGE); 546 return StreamSupport.intStream 547 (new RandomIntsSpliterator 548 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 549 false); 550 } 551 552 /** 553 * Returns a stream producing the given {@code streamSize} number of 554 * pseudorandom {@code long} values. 555 * 556 * @param streamSize the number of values to generate 557 * @return a stream of pseudorandom {@code long} values 558 * @throws IllegalArgumentException if {@code streamSize} is 559 * less than zero 560 * @since 1.8 561 */ longs(long streamSize)562 public LongStream longs(long streamSize) { 563 if (streamSize < 0L) 564 throw new IllegalArgumentException(BAD_SIZE); 565 return StreamSupport.longStream 566 (new RandomLongsSpliterator 567 (0L, streamSize, Long.MAX_VALUE, 0L), 568 false); 569 } 570 571 /** 572 * Returns an effectively unlimited stream of pseudorandom {@code long} 573 * values. 574 * 575 * @implNote This method is implemented to be equivalent to {@code 576 * longs(Long.MAX_VALUE)}. 577 * 578 * @return a stream of pseudorandom {@code long} values 579 * @since 1.8 580 */ longs()581 public LongStream longs() { 582 return StreamSupport.longStream 583 (new RandomLongsSpliterator 584 (0L, Long.MAX_VALUE, Long.MAX_VALUE, 0L), 585 false); 586 } 587 588 /** 589 * Returns a stream producing the given {@code streamSize} number of 590 * pseudorandom {@code long}, each conforming to the given origin 591 * (inclusive) and bound (exclusive). 592 * 593 * @param streamSize the number of values to generate 594 * @param randomNumberOrigin the origin (inclusive) of each random value 595 * @param randomNumberBound the bound (exclusive) of each random value 596 * @return a stream of pseudorandom {@code long} values, 597 * each with the given origin (inclusive) and bound (exclusive) 598 * @throws IllegalArgumentException if {@code streamSize} is 599 * less than zero, or {@code randomNumberOrigin} 600 * is greater than or equal to {@code randomNumberBound} 601 * @since 1.8 602 */ longs(long streamSize, long randomNumberOrigin, long randomNumberBound)603 public LongStream longs(long streamSize, long randomNumberOrigin, 604 long randomNumberBound) { 605 if (streamSize < 0L) 606 throw new IllegalArgumentException(BAD_SIZE); 607 if (randomNumberOrigin >= randomNumberBound) 608 throw new IllegalArgumentException(BAD_RANGE); 609 return StreamSupport.longStream 610 (new RandomLongsSpliterator 611 (0L, streamSize, randomNumberOrigin, randomNumberBound), 612 false); 613 } 614 615 /** 616 * Returns an effectively unlimited stream of pseudorandom {@code 617 * long} values, each conforming to the given origin (inclusive) and bound 618 * (exclusive). 619 * 620 * @implNote This method is implemented to be equivalent to {@code 621 * longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 622 * 623 * @param randomNumberOrigin the origin (inclusive) of each random value 624 * @param randomNumberBound the bound (exclusive) of each random value 625 * @return a stream of pseudorandom {@code long} values, 626 * each with the given origin (inclusive) and bound (exclusive) 627 * @throws IllegalArgumentException if {@code randomNumberOrigin} 628 * is greater than or equal to {@code randomNumberBound} 629 * @since 1.8 630 */ longs(long randomNumberOrigin, long randomNumberBound)631 public LongStream longs(long randomNumberOrigin, long randomNumberBound) { 632 if (randomNumberOrigin >= randomNumberBound) 633 throw new IllegalArgumentException(BAD_RANGE); 634 return StreamSupport.longStream 635 (new RandomLongsSpliterator 636 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 637 false); 638 } 639 640 /** 641 * Returns a stream producing the given {@code streamSize} number of 642 * pseudorandom {@code double} values, each between zero 643 * (inclusive) and one (exclusive). 644 * 645 * @param streamSize the number of values to generate 646 * @return a stream of {@code double} values 647 * @throws IllegalArgumentException if {@code streamSize} is 648 * less than zero 649 * @since 1.8 650 */ doubles(long streamSize)651 public DoubleStream doubles(long streamSize) { 652 if (streamSize < 0L) 653 throw new IllegalArgumentException(BAD_SIZE); 654 return StreamSupport.doubleStream 655 (new RandomDoublesSpliterator 656 (0L, streamSize, Double.MAX_VALUE, 0.0), 657 false); 658 } 659 660 /** 661 * Returns an effectively unlimited stream of pseudorandom {@code 662 * double} values, each between zero (inclusive) and one 663 * (exclusive). 664 * 665 * @implNote This method is implemented to be equivalent to {@code 666 * doubles(Long.MAX_VALUE)}. 667 * 668 * @return a stream of pseudorandom {@code double} values 669 * @since 1.8 670 */ doubles()671 public DoubleStream doubles() { 672 return StreamSupport.doubleStream 673 (new RandomDoublesSpliterator 674 (0L, Long.MAX_VALUE, Double.MAX_VALUE, 0.0), 675 false); 676 } 677 678 /** 679 * Returns a stream producing the given {@code streamSize} number of 680 * pseudorandom {@code double} values, each conforming to the given origin 681 * (inclusive) and bound (exclusive). 682 * 683 * @param streamSize the number of values to generate 684 * @param randomNumberOrigin the origin (inclusive) of each random value 685 * @param randomNumberBound the bound (exclusive) of each random value 686 * @return a stream of pseudorandom {@code double} values, 687 * each with the given origin (inclusive) and bound (exclusive) 688 * @throws IllegalArgumentException if {@code streamSize} is 689 * less than zero 690 * @throws IllegalArgumentException if {@code randomNumberOrigin} 691 * is greater than or equal to {@code randomNumberBound} 692 * @since 1.8 693 */ doubles(long streamSize, double randomNumberOrigin, double randomNumberBound)694 public DoubleStream doubles(long streamSize, double randomNumberOrigin, 695 double randomNumberBound) { 696 if (streamSize < 0L) 697 throw new IllegalArgumentException(BAD_SIZE); 698 if (!(randomNumberOrigin < randomNumberBound)) 699 throw new IllegalArgumentException(BAD_RANGE); 700 return StreamSupport.doubleStream 701 (new RandomDoublesSpliterator 702 (0L, streamSize, randomNumberOrigin, randomNumberBound), 703 false); 704 } 705 706 /** 707 * Returns an effectively unlimited stream of pseudorandom {@code 708 * double} values, each conforming to the given origin (inclusive) and bound 709 * (exclusive). 710 * 711 * @implNote This method is implemented to be equivalent to {@code 712 * doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. 713 * 714 * @param randomNumberOrigin the origin (inclusive) of each random value 715 * @param randomNumberBound the bound (exclusive) of each random value 716 * @return a stream of pseudorandom {@code double} values, 717 * each with the given origin (inclusive) and bound (exclusive) 718 * @throws IllegalArgumentException if {@code randomNumberOrigin} 719 * is greater than or equal to {@code randomNumberBound} 720 * @since 1.8 721 */ doubles(double randomNumberOrigin, double randomNumberBound)722 public DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { 723 if (!(randomNumberOrigin < randomNumberBound)) 724 throw new IllegalArgumentException(BAD_RANGE); 725 return StreamSupport.doubleStream 726 (new RandomDoublesSpliterator 727 (0L, Long.MAX_VALUE, randomNumberOrigin, randomNumberBound), 728 false); 729 } 730 731 /** 732 * Spliterator for int streams. We multiplex the four int 733 * versions into one class by treating a bound less than origin as 734 * unbounded, and also by treating "infinite" as equivalent to 735 * Long.MAX_VALUE. For splits, it uses the standard divide-by-two 736 * approach. The long and double versions of this class are 737 * identical except for types. 738 */ 739 private static final class RandomIntsSpliterator 740 implements Spliterator.OfInt { 741 long index; 742 final long fence; 743 final int origin; 744 final int bound; RandomIntsSpliterator(long index, long fence, int origin, int bound)745 RandomIntsSpliterator(long index, long fence, 746 int origin, int bound) { 747 this.index = index; this.fence = fence; 748 this.origin = origin; this.bound = bound; 749 } 750 trySplit()751 public RandomIntsSpliterator trySplit() { 752 long i = index, m = (i + fence) >>> 1; 753 return (m <= i) ? null : 754 new RandomIntsSpliterator(i, index = m, origin, bound); 755 } 756 estimateSize()757 public long estimateSize() { 758 return fence - index; 759 } 760 characteristics()761 public int characteristics() { 762 return (Spliterator.SIZED | Spliterator.SUBSIZED | 763 Spliterator.NONNULL | Spliterator.IMMUTABLE); 764 } 765 tryAdvance(IntConsumer consumer)766 public boolean tryAdvance(IntConsumer consumer) { 767 if (consumer == null) throw new NullPointerException(); 768 long i = index, f = fence; 769 if (i < f) { 770 consumer.accept(ThreadLocalRandom.current().internalNextInt(origin, bound)); 771 index = i + 1; 772 return true; 773 } 774 return false; 775 } 776 forEachRemaining(IntConsumer consumer)777 public void forEachRemaining(IntConsumer consumer) { 778 if (consumer == null) throw new NullPointerException(); 779 long i = index, f = fence; 780 if (i < f) { 781 index = f; 782 int o = origin, b = bound; 783 ThreadLocalRandom rng = ThreadLocalRandom.current(); 784 do { 785 consumer.accept(rng.internalNextInt(o, b)); 786 } while (++i < f); 787 } 788 } 789 } 790 791 /** 792 * Spliterator for long streams. 793 */ 794 private static final class RandomLongsSpliterator 795 implements Spliterator.OfLong { 796 long index; 797 final long fence; 798 final long origin; 799 final long bound; RandomLongsSpliterator(long index, long fence, long origin, long bound)800 RandomLongsSpliterator(long index, long fence, 801 long origin, long bound) { 802 this.index = index; this.fence = fence; 803 this.origin = origin; this.bound = bound; 804 } 805 trySplit()806 public RandomLongsSpliterator trySplit() { 807 long i = index, m = (i + fence) >>> 1; 808 return (m <= i) ? null : 809 new RandomLongsSpliterator(i, index = m, origin, bound); 810 } 811 estimateSize()812 public long estimateSize() { 813 return fence - index; 814 } 815 characteristics()816 public int characteristics() { 817 return (Spliterator.SIZED | Spliterator.SUBSIZED | 818 Spliterator.NONNULL | Spliterator.IMMUTABLE); 819 } 820 tryAdvance(LongConsumer consumer)821 public boolean tryAdvance(LongConsumer consumer) { 822 if (consumer == null) throw new NullPointerException(); 823 long i = index, f = fence; 824 if (i < f) { 825 consumer.accept(ThreadLocalRandom.current().internalNextLong(origin, bound)); 826 index = i + 1; 827 return true; 828 } 829 return false; 830 } 831 forEachRemaining(LongConsumer consumer)832 public void forEachRemaining(LongConsumer consumer) { 833 if (consumer == null) throw new NullPointerException(); 834 long i = index, f = fence; 835 if (i < f) { 836 index = f; 837 long o = origin, b = bound; 838 ThreadLocalRandom rng = ThreadLocalRandom.current(); 839 do { 840 consumer.accept(rng.internalNextLong(o, b)); 841 } while (++i < f); 842 } 843 } 844 845 } 846 847 /** 848 * Spliterator for double streams. 849 */ 850 private static final class RandomDoublesSpliterator 851 implements Spliterator.OfDouble { 852 long index; 853 final long fence; 854 final double origin; 855 final double bound; RandomDoublesSpliterator(long index, long fence, double origin, double bound)856 RandomDoublesSpliterator(long index, long fence, 857 double origin, double bound) { 858 this.index = index; this.fence = fence; 859 this.origin = origin; this.bound = bound; 860 } 861 trySplit()862 public RandomDoublesSpliterator trySplit() { 863 long i = index, m = (i + fence) >>> 1; 864 return (m <= i) ? null : 865 new RandomDoublesSpliterator(i, index = m, origin, bound); 866 } 867 estimateSize()868 public long estimateSize() { 869 return fence - index; 870 } 871 characteristics()872 public int characteristics() { 873 return (Spliterator.SIZED | Spliterator.SUBSIZED | 874 Spliterator.NONNULL | Spliterator.IMMUTABLE); 875 } 876 tryAdvance(DoubleConsumer consumer)877 public boolean tryAdvance(DoubleConsumer consumer) { 878 if (consumer == null) throw new NullPointerException(); 879 long i = index, f = fence; 880 if (i < f) { 881 consumer.accept(ThreadLocalRandom.current().internalNextDouble(origin, bound)); 882 index = i + 1; 883 return true; 884 } 885 return false; 886 } 887 forEachRemaining(DoubleConsumer consumer)888 public void forEachRemaining(DoubleConsumer consumer) { 889 if (consumer == null) throw new NullPointerException(); 890 long i = index, f = fence; 891 if (i < f) { 892 index = f; 893 double o = origin, b = bound; 894 ThreadLocalRandom rng = ThreadLocalRandom.current(); 895 do { 896 consumer.accept(rng.internalNextDouble(o, b)); 897 } while (++i < f); 898 } 899 } 900 } 901 902 903 // Within-package utilities 904 905 /* 906 * Descriptions of the usages of the methods below can be found in 907 * the classes that use them. Briefly, a thread's "probe" value is 908 * a non-zero hash code that (probably) does not collide with 909 * other existing threads with respect to any power of two 910 * collision space. When it does collide, it is pseudo-randomly 911 * adjusted (using a Marsaglia XorShift). The nextSecondarySeed 912 * method is used in the same contexts as ThreadLocalRandom, but 913 * only for transient usages such as random adaptive spin/block 914 * sequences for which a cheap RNG suffices and for which it could 915 * in principle disrupt user-visible statistical properties of the 916 * main ThreadLocalRandom if we were to use it. 917 * 918 * Note: Because of package-protection issues, versions of some 919 * these methods also appear in some subpackage classes. 920 */ 921 922 /** 923 * Returns the probe value for the current thread without forcing 924 * initialization. Note that invoking ThreadLocalRandom.current() 925 * can be used to force initialization on zero return. 926 */ getProbe()927 static final int getProbe() { 928 return U.getInt(Thread.currentThread(), PROBE); 929 } 930 931 /** 932 * Pseudo-randomly advances and records the given probe value for the 933 * given thread. 934 */ advanceProbe(int probe)935 static final int advanceProbe(int probe) { 936 probe ^= probe << 13; // xorshift 937 probe ^= probe >>> 17; 938 probe ^= probe << 5; 939 U.putInt(Thread.currentThread(), PROBE, probe); 940 return probe; 941 } 942 943 /** 944 * Returns the pseudo-randomly initialized or updated secondary seed. 945 */ nextSecondarySeed()946 static final int nextSecondarySeed() { 947 int r; 948 Thread t = Thread.currentThread(); 949 if ((r = U.getInt(t, SECONDARY)) != 0) { 950 r ^= r << 13; // xorshift 951 r ^= r >>> 17; 952 r ^= r << 5; 953 } 954 else if ((r = mix32(seeder.getAndAdd(SEEDER_INCREMENT))) == 0) 955 r = 1; // avoid zero 956 U.putInt(t, SECONDARY, r); 957 return r; 958 } 959 960 // Serialization support 961 962 private static final long serialVersionUID = -5851777807851030925L; 963 964 /** 965 * @serialField rnd long 966 * seed for random computations 967 * @serialField initialized boolean 968 * always true 969 */ 970 private static final ObjectStreamField[] serialPersistentFields = { 971 new ObjectStreamField("rnd", long.class), 972 new ObjectStreamField("initialized", boolean.class), 973 }; 974 975 /** 976 * Saves the {@code ThreadLocalRandom} to a stream (that is, serializes it). 977 * @param s the stream 978 * @throws java.io.IOException if an I/O error occurs 979 */ writeObject(java.io.ObjectOutputStream s)980 private void writeObject(java.io.ObjectOutputStream s) 981 throws java.io.IOException { 982 983 java.io.ObjectOutputStream.PutField fields = s.putFields(); 984 fields.put("rnd", U.getLong(Thread.currentThread(), SEED)); 985 fields.put("initialized", true); 986 s.writeFields(); 987 } 988 989 /** 990 * Returns the {@link #current() current} thread's {@code ThreadLocalRandom}. 991 * @return the {@link #current() current} thread's {@code ThreadLocalRandom} 992 */ readResolve()993 private Object readResolve() { 994 return current(); 995 } 996 997 // Static initialization 998 999 /** 1000 * The seed increment. 1001 */ 1002 private static final long GAMMA = 0x9e3779b97f4a7c15L; 1003 1004 /** 1005 * The increment for generating probe values. 1006 */ 1007 private static final int PROBE_INCREMENT = 0x9e3779b9; 1008 1009 /** 1010 * The increment of seeder per new instance. 1011 */ 1012 private static final long SEEDER_INCREMENT = 0xbb67ae8584caa73bL; 1013 1014 // Constants from SplittableRandom 1015 private static final double DOUBLE_UNIT = 0x1.0p-53; // 1.0 / (1L << 53) 1016 private static final float FLOAT_UNIT = 0x1.0p-24f; // 1.0f / (1 << 24) 1017 1018 // IllegalArgumentException messages 1019 static final String BAD_BOUND = "bound must be positive"; 1020 static final String BAD_RANGE = "bound must be greater than origin"; 1021 static final String BAD_SIZE = "size must be non-negative"; 1022 1023 // Unsafe mechanics 1024 private static final sun.misc.Unsafe U = sun.misc.Unsafe.getUnsafe(); 1025 private static final long SEED; 1026 private static final long PROBE; 1027 private static final long SECONDARY; 1028 static { 1029 try { 1030 SEED = U.objectFieldOffset 1031 (Thread.class.getDeclaredField("threadLocalRandomSeed")); 1032 PROBE = U.objectFieldOffset 1033 (Thread.class.getDeclaredField("threadLocalRandomProbe")); 1034 SECONDARY = U.objectFieldOffset 1035 (Thread.class.getDeclaredField("threadLocalRandomSecondarySeed")); 1036 } catch (ReflectiveOperationException e) { 1037 throw new Error(e); 1038 } 1039 } 1040 1041 /** Rarely-used holder for the second of a pair of Gaussians */ 1042 private static final ThreadLocal<Double> nextLocalGaussian = 1043 new ThreadLocal<>(); 1044 1045 /** Generates per-thread initialization/probe field */ 1046 private static final AtomicInteger probeGenerator = new AtomicInteger(); 1047 1048 /** The common ThreadLocalRandom */ 1049 static final ThreadLocalRandom instance = new ThreadLocalRandom(); 1050 1051 /** 1052 * The next seed for default constructors. 1053 */ 1054 private static final AtomicLong seeder 1055 = new AtomicLong(mix64(System.currentTimeMillis()) ^ 1056 mix64(System.nanoTime())); 1057 1058 // at end of <clinit> to survive static initialization circularity 1059 static { 1060 if (java.security.AccessController.doPrivileged( 1061 new java.security.PrivilegedAction<Boolean>() { 1062 public Boolean run() { 1063 return Boolean.getBoolean("java.util.secureRandomSeed"); 1064 }})) { 1065 byte[] seedBytes = java.security.SecureRandom.getSeed(8); 1066 long s = (long)seedBytes[0] & 0xffL; 1067 for (int i = 1; i < 8; ++i) 1068 s = (s << 8) | ((long)seedBytes[i] & 0xffL); 1069 seeder.set(s); 1070 } 1071 } 1072 } 1073