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