1 /* 2 * Copyright (c) 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 package java.util.stream; 26 27 import java.math.BigInteger; 28 import java.nio.charset.Charset; 29 import java.util.Arrays; 30 import java.util.Collection; 31 import java.util.LongSummaryStatistics; 32 import java.util.Objects; 33 import java.util.OptionalDouble; 34 import java.util.OptionalLong; 35 import java.util.PrimitiveIterator; 36 import java.util.Spliterator; 37 import java.util.Spliterators; 38 import java.util.concurrent.ConcurrentHashMap; 39 import java.util.function.BiConsumer; 40 import java.util.function.Function; 41 import java.util.function.LongBinaryOperator; 42 import java.util.function.LongConsumer; 43 import java.util.function.LongFunction; 44 import java.util.function.LongPredicate; 45 import java.util.function.LongSupplier; 46 import java.util.function.LongToDoubleFunction; 47 import java.util.function.LongToIntFunction; 48 import java.util.function.LongUnaryOperator; 49 import java.util.function.ObjLongConsumer; 50 import java.util.function.Supplier; 51 52 /** 53 * A sequence of primitive long-valued elements supporting sequential and parallel 54 * aggregate operations. This is the {@code long} primitive specialization of 55 * {@link Stream}. 56 * 57 * <p>The following example illustrates an aggregate operation using 58 * {@link Stream} and {@link LongStream}, computing the sum of the weights of the 59 * red widgets: 60 * 61 * <pre>{@code 62 * long sum = widgets.stream() 63 * .filter(w -> w.getColor() == RED) 64 * .mapToLong(w -> w.getWeight()) 65 * .sum(); 66 * }</pre> 67 * 68 * See the class documentation for {@link Stream} and the package documentation 69 * for <a href="package-summary.html">java.util.stream</a> for additional 70 * specification of streams, stream operations, stream pipelines, and 71 * parallelism. 72 * 73 * @since 1.8 74 * @see Stream 75 * @see <a href="package-summary.html">java.util.stream</a> 76 */ 77 public interface LongStream extends BaseStream<Long, LongStream> { 78 79 /** 80 * Returns a stream consisting of the elements of this stream that match 81 * the given predicate. 82 * 83 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 84 * operation</a>. 85 * 86 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 87 * <a href="package-summary.html#Statelessness">stateless</a> 88 * predicate to apply to each element to determine if it 89 * should be included 90 * @return the new stream 91 */ filter(LongPredicate predicate)92 LongStream filter(LongPredicate predicate); 93 94 /** 95 * Returns a stream consisting of the results of applying the given 96 * function to the elements of this stream. 97 * 98 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 99 * operation</a>. 100 * 101 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 102 * <a href="package-summary.html#Statelessness">stateless</a> 103 * function to apply to each element 104 * @return the new stream 105 */ map(LongUnaryOperator mapper)106 LongStream map(LongUnaryOperator mapper); 107 108 /** 109 * Returns an object-valued {@code Stream} consisting of the results of 110 * applying the given function to the elements of this stream. 111 * 112 * <p>This is an <a href="package-summary.html#StreamOps"> 113 * intermediate operation</a>. 114 * 115 * @param <U> the element type of the new stream 116 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 117 * <a href="package-summary.html#Statelessness">stateless</a> 118 * function to apply to each element 119 * @return the new stream 120 */ mapToObj(LongFunction<? extends U> mapper)121 <U> Stream<U> mapToObj(LongFunction<? extends U> mapper); 122 123 /** 124 * Returns an {@code IntStream} consisting of the results of applying the 125 * given function to the elements of this stream. 126 * 127 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 128 * operation</a>. 129 * 130 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 131 * <a href="package-summary.html#Statelessness">stateless</a> 132 * function to apply to each element 133 * @return the new stream 134 */ mapToInt(LongToIntFunction mapper)135 IntStream mapToInt(LongToIntFunction mapper); 136 137 /** 138 * Returns a {@code DoubleStream} consisting of the results of applying the 139 * given function to the elements of this stream. 140 * 141 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 142 * operation</a>. 143 * 144 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 145 * <a href="package-summary.html#Statelessness">stateless</a> 146 * function to apply to each element 147 * @return the new stream 148 */ mapToDouble(LongToDoubleFunction mapper)149 DoubleStream mapToDouble(LongToDoubleFunction mapper); 150 151 /** 152 * Returns a stream consisting of the results of replacing each element of 153 * this stream with the contents of a mapped stream produced by applying 154 * the provided mapping function to each element. Each mapped stream is 155 * {@link java.util.stream.BaseStream#close() closed} after its contents 156 * have been placed into this stream. (If a mapped stream is {@code null} 157 * an empty stream is used, instead.) 158 * 159 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 160 * operation</a>. 161 * 162 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 163 * <a href="package-summary.html#Statelessness">stateless</a> 164 * function to apply to each element which produces a 165 * {@code LongStream} of new values 166 * @return the new stream 167 * @see Stream#flatMap(Function) 168 */ flatMap(LongFunction<? extends LongStream> mapper)169 LongStream flatMap(LongFunction<? extends LongStream> mapper); 170 171 /** 172 * Returns a stream consisting of the distinct elements of this stream. 173 * 174 * <p>This is a <a href="package-summary.html#StreamOps">stateful 175 * intermediate operation</a>. 176 * 177 * @return the new stream 178 */ distinct()179 LongStream distinct(); 180 181 /** 182 * Returns a stream consisting of the elements of this stream in sorted 183 * order. 184 * 185 * <p>This is a <a href="package-summary.html#StreamOps">stateful 186 * intermediate operation</a>. 187 * 188 * @return the new stream 189 */ sorted()190 LongStream sorted(); 191 192 /** 193 * Returns a stream consisting of the elements of this stream, additionally 194 * performing the provided action on each element as elements are consumed 195 * from the resulting stream. 196 * 197 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 198 * operation</a>. 199 * 200 * <p>For parallel stream pipelines, the action may be called at 201 * whatever time and in whatever thread the element is made available by the 202 * upstream operation. If the action modifies shared state, 203 * it is responsible for providing the required synchronization. 204 * 205 * @apiNote This method exists mainly to support debugging, where you want 206 * to see the elements as they flow past a certain point in a pipeline: 207 * <pre>{@code 208 * LongStream.of(1, 2, 3, 4) 209 * .filter(e -> e > 2) 210 * .peek(e -> System.out.println("Filtered value: " + e)) 211 * .map(e -> e * e) 212 * .peek(e -> System.out.println("Mapped value: " + e)) 213 * .sum(); 214 * }</pre> 215 * 216 * @param action a <a href="package-summary.html#NonInterference"> 217 * non-interfering</a> action to perform on the elements as 218 * they are consumed from the stream 219 * @return the new stream 220 */ peek(LongConsumer action)221 LongStream peek(LongConsumer action); 222 223 /** 224 * Returns a stream consisting of the elements of this stream, truncated 225 * to be no longer than {@code maxSize} in length. 226 * 227 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 228 * stateful intermediate operation</a>. 229 * 230 * @apiNote 231 * While {@code limit()} is generally a cheap operation on sequential 232 * stream pipelines, it can be quite expensive on ordered parallel pipelines, 233 * especially for large values of {@code maxSize}, since {@code limit(n)} 234 * is constrained to return not just any <em>n</em> elements, but the 235 * <em>first n</em> elements in the encounter order. Using an unordered 236 * stream source (such as {@link #generate(LongSupplier)}) or removing the 237 * ordering constraint with {@link #unordered()} may result in significant 238 * speedups of {@code limit()} in parallel pipelines, if the semantics of 239 * your situation permit. If consistency with encounter order is required, 240 * and you are experiencing poor performance or memory utilization with 241 * {@code limit()} in parallel pipelines, switching to sequential execution 242 * with {@link #sequential()} may improve performance. 243 * 244 * @param maxSize the number of elements the stream should be limited to 245 * @return the new stream 246 * @throws IllegalArgumentException if {@code maxSize} is negative 247 */ limit(long maxSize)248 LongStream limit(long maxSize); 249 250 /** 251 * Returns a stream consisting of the remaining elements of this stream 252 * after discarding the first {@code n} elements of the stream. 253 * If this stream contains fewer than {@code n} elements then an 254 * empty stream will be returned. 255 * 256 * <p>This is a <a href="package-summary.html#StreamOps">stateful 257 * intermediate operation</a>. 258 * 259 * @apiNote 260 * While {@code skip()} is generally a cheap operation on sequential 261 * stream pipelines, it can be quite expensive on ordered parallel pipelines, 262 * especially for large values of {@code n}, since {@code skip(n)} 263 * is constrained to skip not just any <em>n</em> elements, but the 264 * <em>first n</em> elements in the encounter order. Using an unordered 265 * stream source (such as {@link #generate(LongSupplier)}) or removing the 266 * ordering constraint with {@link #unordered()} may result in significant 267 * speedups of {@code skip()} in parallel pipelines, if the semantics of 268 * your situation permit. If consistency with encounter order is required, 269 * and you are experiencing poor performance or memory utilization with 270 * {@code skip()} in parallel pipelines, switching to sequential execution 271 * with {@link #sequential()} may improve performance. 272 * 273 * @param n the number of leading elements to skip 274 * @return the new stream 275 * @throws IllegalArgumentException if {@code n} is negative 276 */ skip(long n)277 LongStream skip(long n); 278 279 /** 280 * Performs an action for each element of this stream. 281 * 282 * <p>This is a <a href="package-summary.html#StreamOps">terminal 283 * operation</a>. 284 * 285 * <p>For parallel stream pipelines, this operation does <em>not</em> 286 * guarantee to respect the encounter order of the stream, as doing so 287 * would sacrifice the benefit of parallelism. For any given element, the 288 * action may be performed at whatever time and in whatever thread the 289 * library chooses. If the action accesses shared state, it is 290 * responsible for providing the required synchronization. 291 * 292 * @param action a <a href="package-summary.html#NonInterference"> 293 * non-interfering</a> action to perform on the elements 294 */ forEach(LongConsumer action)295 void forEach(LongConsumer action); 296 297 /** 298 * Performs an action for each element of this stream, guaranteeing that 299 * each element is processed in encounter order for streams that have a 300 * defined encounter order. 301 * 302 * <p>This is a <a href="package-summary.html#StreamOps">terminal 303 * operation</a>. 304 * 305 * @param action a <a href="package-summary.html#NonInterference"> 306 * non-interfering</a> action to perform on the elements 307 * @see #forEach(LongConsumer) 308 */ forEachOrdered(LongConsumer action)309 void forEachOrdered(LongConsumer action); 310 311 /** 312 * Returns an array containing the elements of this stream. 313 * 314 * <p>This is a <a href="package-summary.html#StreamOps">terminal 315 * operation</a>. 316 * 317 * @return an array containing the elements of this stream 318 */ toArray()319 long[] toArray(); 320 321 /** 322 * Performs a <a href="package-summary.html#Reduction">reduction</a> on the 323 * elements of this stream, using the provided identity value and an 324 * <a href="package-summary.html#Associativity">associative</a> 325 * accumulation function, and returns the reduced value. This is equivalent 326 * to: 327 * <pre>{@code 328 * long result = identity; 329 * for (long element : this stream) 330 * result = accumulator.applyAsLong(result, element) 331 * return result; 332 * }</pre> 333 * 334 * but is not constrained to execute sequentially. 335 * 336 * <p>The {@code identity} value must be an identity for the accumulator 337 * function. This means that for all {@code x}, 338 * {@code accumulator.apply(identity, x)} is equal to {@code x}. 339 * The {@code accumulator} function must be an 340 * <a href="package-summary.html#Associativity">associative</a> function. 341 * 342 * <p>This is a <a href="package-summary.html#StreamOps">terminal 343 * operation</a>. 344 * 345 * @apiNote Sum, min, max, and average are all special cases of reduction. 346 * Summing a stream of numbers can be expressed as: 347 * 348 * <pre>{@code 349 * long sum = integers.reduce(0, (a, b) -> a+b); 350 * }</pre> 351 * 352 * or more compactly: 353 * 354 * <pre>{@code 355 * long sum = integers.reduce(0, Long::sum); 356 * }</pre> 357 * 358 * <p>While this may seem a more roundabout way to perform an aggregation 359 * compared to simply mutating a running total in a loop, reduction 360 * operations parallelize more gracefully, without needing additional 361 * synchronization and with greatly reduced risk of data races. 362 * 363 * @param identity the identity value for the accumulating function 364 * @param op an <a href="package-summary.html#Associativity">associative</a>, 365 * <a href="package-summary.html#NonInterference">non-interfering</a>, 366 * <a href="package-summary.html#Statelessness">stateless</a> 367 * function for combining two values 368 * @return the result of the reduction 369 * @see #sum() 370 * @see #min() 371 * @see #max() 372 * @see #average() 373 */ reduce(long identity, LongBinaryOperator op)374 long reduce(long identity, LongBinaryOperator op); 375 376 /** 377 * Performs a <a href="package-summary.html#Reduction">reduction</a> on the 378 * elements of this stream, using an 379 * <a href="package-summary.html#Associativity">associative</a> accumulation 380 * function, and returns an {@code OptionalLong} describing the reduced value, 381 * if any. This is equivalent to: 382 * <pre>{@code 383 * boolean foundAny = false; 384 * long result = null; 385 * for (long element : this stream) { 386 * if (!foundAny) { 387 * foundAny = true; 388 * result = element; 389 * } 390 * else 391 * result = accumulator.applyAsLong(result, element); 392 * } 393 * return foundAny ? OptionalLong.of(result) : OptionalLong.empty(); 394 * }</pre> 395 * 396 * but is not constrained to execute sequentially. 397 * 398 * <p>The {@code accumulator} function must be an 399 * <a href="package-summary.html#Associativity">associative</a> function. 400 * 401 * <p>This is a <a href="package-summary.html#StreamOps">terminal 402 * operation</a>. 403 * 404 * @param op an <a href="package-summary.html#Associativity">associative</a>, 405 * <a href="package-summary.html#NonInterference">non-interfering</a>, 406 * <a href="package-summary.html#Statelessness">stateless</a> 407 * function for combining two values 408 * @return the result of the reduction 409 * @see #reduce(long, LongBinaryOperator) 410 */ reduce(LongBinaryOperator op)411 OptionalLong reduce(LongBinaryOperator op); 412 413 /** 414 * Performs a <a href="package-summary.html#MutableReduction">mutable 415 * reduction</a> operation on the elements of this stream. A mutable 416 * reduction is one in which the reduced value is a mutable result container, 417 * such as an {@code ArrayList}, and elements are incorporated by updating 418 * the state of the result rather than by replacing the result. This 419 * produces a result equivalent to: 420 * <pre>{@code 421 * R result = supplier.get(); 422 * for (long element : this stream) 423 * accumulator.accept(result, element); 424 * return result; 425 * }</pre> 426 * 427 * <p>Like {@link #reduce(long, LongBinaryOperator)}, {@code collect} operations 428 * can be parallelized without requiring additional synchronization. 429 * 430 * <p>This is a <a href="package-summary.html#StreamOps">terminal 431 * operation</a>. 432 * 433 * @param <R> type of the result 434 * @param supplier a function that creates a new result container. For a 435 * parallel execution, this function may be called 436 * multiple times and must return a fresh value each time. 437 * @param accumulator an <a href="package-summary.html#Associativity">associative</a>, 438 * <a href="package-summary.html#NonInterference">non-interfering</a>, 439 * <a href="package-summary.html#Statelessness">stateless</a> 440 * function for incorporating an additional element into a result 441 * @param combiner an <a href="package-summary.html#Associativity">associative</a>, 442 * <a href="package-summary.html#NonInterference">non-interfering</a>, 443 * <a href="package-summary.html#Statelessness">stateless</a> 444 * function for combining two values, which must be 445 * compatible with the accumulator function 446 * @return the result of the reduction 447 * @see Stream#collect(Supplier, BiConsumer, BiConsumer) 448 */ collect(Supplier<R> supplier, ObjLongConsumer<R> accumulator, BiConsumer<R, R> combiner)449 <R> R collect(Supplier<R> supplier, 450 ObjLongConsumer<R> accumulator, 451 BiConsumer<R, R> combiner); 452 453 /** 454 * Returns the sum of elements in this stream. This is a special case 455 * of a <a href="package-summary.html#Reduction">reduction</a> 456 * and is equivalent to: 457 * <pre>{@code 458 * return reduce(0, Long::sum); 459 * }</pre> 460 * 461 * <p>This is a <a href="package-summary.html#StreamOps">terminal 462 * operation</a>. 463 * 464 * @return the sum of elements in this stream 465 */ sum()466 long sum(); 467 468 /** 469 * Returns an {@code OptionalLong} describing the minimum element of this 470 * stream, or an empty optional if this stream is empty. This is a special 471 * case of a <a href="package-summary.html#Reduction">reduction</a> 472 * and is equivalent to: 473 * <pre>{@code 474 * return reduce(Long::min); 475 * }</pre> 476 * 477 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. 478 * 479 * @return an {@code OptionalLong} containing the minimum element of this 480 * stream, or an empty {@code OptionalLong} if the stream is empty 481 */ min()482 OptionalLong min(); 483 484 /** 485 * Returns an {@code OptionalLong} describing the maximum element of this 486 * stream, or an empty optional if this stream is empty. This is a special 487 * case of a <a href="package-summary.html#Reduction">reduction</a> 488 * and is equivalent to: 489 * <pre>{@code 490 * return reduce(Long::max); 491 * }</pre> 492 * 493 * <p>This is a <a href="package-summary.html#StreamOps">terminal 494 * operation</a>. 495 * 496 * @return an {@code OptionalLong} containing the maximum element of this 497 * stream, or an empty {@code OptionalLong} if the stream is empty 498 */ max()499 OptionalLong max(); 500 501 /** 502 * Returns the count of elements in this stream. This is a special case of 503 * a <a href="package-summary.html#Reduction">reduction</a> and is 504 * equivalent to: 505 * <pre>{@code 506 * return map(e -> 1L).sum(); 507 * }</pre> 508 * 509 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. 510 * 511 * @return the count of elements in this stream 512 */ count()513 long count(); 514 515 /** 516 * Returns an {@code OptionalDouble} describing the arithmetic mean of elements of 517 * this stream, or an empty optional if this stream is empty. This is a 518 * special case of a 519 * <a href="package-summary.html#Reduction">reduction</a>. 520 * 521 * <p>This is a <a href="package-summary.html#StreamOps">terminal 522 * operation</a>. 523 * 524 * @return an {@code OptionalDouble} containing the average element of this 525 * stream, or an empty optional if the stream is empty 526 */ average()527 OptionalDouble average(); 528 529 /** 530 * Returns a {@code LongSummaryStatistics} describing various summary data 531 * about the elements of this stream. This is a special case of a 532 * <a href="package-summary.html#Reduction">reduction</a>. 533 * 534 * <p>This is a <a href="package-summary.html#StreamOps">terminal 535 * operation</a>. 536 * 537 * @return a {@code LongSummaryStatistics} describing various summary data 538 * about the elements of this stream 539 */ summaryStatistics()540 LongSummaryStatistics summaryStatistics(); 541 542 /** 543 * Returns whether any elements of this stream match the provided 544 * predicate. May not evaluate the predicate on all elements if not 545 * necessary for determining the result. If the stream is empty then 546 * {@code false} is returned and the predicate is not evaluated. 547 * 548 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 549 * terminal operation</a>. 550 * 551 * @apiNote 552 * This method evaluates the <em>existential quantification</em> of the 553 * predicate over the elements of the stream (for some x P(x)). 554 * 555 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 556 * <a href="package-summary.html#Statelessness">stateless</a> 557 * predicate to apply to elements of this stream 558 * @return {@code true} if any elements of the stream match the provided 559 * predicate, otherwise {@code false} 560 */ anyMatch(LongPredicate predicate)561 boolean anyMatch(LongPredicate predicate); 562 563 /** 564 * Returns whether all elements of this stream match the provided predicate. 565 * May not evaluate the predicate on all elements if not necessary for 566 * determining the result. If the stream is empty then {@code true} is 567 * returned and the predicate is not evaluated. 568 * 569 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 570 * terminal operation</a>. 571 * 572 * @apiNote 573 * This method evaluates the <em>universal quantification</em> of the 574 * predicate over the elements of the stream (for all x P(x)). If the 575 * stream is empty, the quantification is said to be <em>vacuously 576 * satisfied</em> and is always {@code true} (regardless of P(x)). 577 * 578 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 579 * <a href="package-summary.html#Statelessness">stateless</a> 580 * predicate to apply to elements of this stream 581 * @return {@code true} if either all elements of the stream match the 582 * provided predicate or the stream is empty, otherwise {@code false} 583 */ allMatch(LongPredicate predicate)584 boolean allMatch(LongPredicate predicate); 585 586 /** 587 * Returns whether no elements of this stream match the provided predicate. 588 * May not evaluate the predicate on all elements if not necessary for 589 * determining the result. If the stream is empty then {@code true} is 590 * returned and the predicate is not evaluated. 591 * 592 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 593 * terminal operation</a>. 594 * 595 * @apiNote 596 * This method evaluates the <em>universal quantification</em> of the 597 * negated predicate over the elements of the stream (for all x ~P(x)). If 598 * the stream is empty, the quantification is said to be vacuously satisfied 599 * and is always {@code true}, regardless of P(x). 600 * 601 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 602 * <a href="package-summary.html#Statelessness">stateless</a> 603 * predicate to apply to elements of this stream 604 * @return {@code true} if either no elements of the stream match the 605 * provided predicate or the stream is empty, otherwise {@code false} 606 */ noneMatch(LongPredicate predicate)607 boolean noneMatch(LongPredicate predicate); 608 609 /** 610 * Returns an {@link OptionalLong} describing the first element of this 611 * stream, or an empty {@code OptionalLong} if the stream is empty. If the 612 * stream has no encounter order, then any element may be returned. 613 * 614 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 615 * terminal operation</a>. 616 * 617 * @return an {@code OptionalLong} describing the first element of this 618 * stream, or an empty {@code OptionalLong} if the stream is empty 619 */ findFirst()620 OptionalLong findFirst(); 621 622 /** 623 * Returns an {@link OptionalLong} describing some element of the stream, or 624 * an empty {@code OptionalLong} if the stream is empty. 625 * 626 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 627 * terminal operation</a>. 628 * 629 * <p>The behavior of this operation is explicitly nondeterministic; it is 630 * free to select any element in the stream. This is to allow for maximal 631 * performance in parallel operations; the cost is that multiple invocations 632 * on the same source may not return the same result. (If a stable result 633 * is desired, use {@link #findFirst()} instead.) 634 * 635 * @return an {@code OptionalLong} describing some element of this stream, 636 * or an empty {@code OptionalLong} if the stream is empty 637 * @see #findFirst() 638 */ findAny()639 OptionalLong findAny(); 640 641 /** 642 * Returns a {@code DoubleStream} consisting of the elements of this stream, 643 * converted to {@code double}. 644 * 645 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 646 * operation</a>. 647 * 648 * @return a {@code DoubleStream} consisting of the elements of this stream, 649 * converted to {@code double} 650 */ asDoubleStream()651 DoubleStream asDoubleStream(); 652 653 /** 654 * Returns a {@code Stream} consisting of the elements of this stream, 655 * each boxed to a {@code Long}. 656 * 657 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 658 * operation</a>. 659 * 660 * @return a {@code Stream} consistent of the elements of this stream, 661 * each boxed to {@code Long} 662 */ boxed()663 Stream<Long> boxed(); 664 665 @Override sequential()666 LongStream sequential(); 667 668 @Override parallel()669 LongStream parallel(); 670 671 @Override iterator()672 PrimitiveIterator.OfLong iterator(); 673 674 @Override spliterator()675 Spliterator.OfLong spliterator(); 676 677 // Static factories 678 679 /** 680 * Returns a builder for a {@code LongStream}. 681 * 682 * @return a stream builder 683 */ builder()684 public static Builder builder() { 685 return new Streams.LongStreamBuilderImpl(); 686 } 687 688 /** 689 * Returns an empty sequential {@code LongStream}. 690 * 691 * @return an empty sequential stream 692 */ empty()693 public static LongStream empty() { 694 return StreamSupport.longStream(Spliterators.emptyLongSpliterator(), false); 695 } 696 697 /** 698 * Returns a sequential {@code LongStream} containing a single element. 699 * 700 * @param t the single element 701 * @return a singleton sequential stream 702 */ of(long t)703 public static LongStream of(long t) { 704 return StreamSupport.longStream(new Streams.LongStreamBuilderImpl(t), false); 705 } 706 707 /** 708 * Returns a sequential ordered stream whose elements are the specified values. 709 * 710 * @param values the elements of the new stream 711 * @return the new stream 712 */ of(long... values)713 public static LongStream of(long... values) { 714 return Arrays.stream(values); 715 } 716 717 /** 718 * Returns an infinite sequential ordered {@code LongStream} produced by iterative 719 * application of a function {@code f} to an initial element {@code seed}, 720 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)}, 721 * {@code f(f(seed))}, etc. 722 * 723 * <p>The first element (position {@code 0}) in the {@code LongStream} will 724 * be the provided {@code seed}. For {@code n > 0}, the element at position 725 * {@code n}, will be the result of applying the function {@code f} to the 726 * element at position {@code n - 1}. 727 * 728 * @param seed the initial element 729 * @param f a function to be applied to to the previous element to produce 730 * a new element 731 * @return a new sequential {@code LongStream} 732 */ iterate(final long seed, final LongUnaryOperator f)733 public static LongStream iterate(final long seed, final LongUnaryOperator f) { 734 Objects.requireNonNull(f); 735 final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() { 736 long t = seed; 737 738 @Override 739 public boolean hasNext() { 740 return true; 741 } 742 743 @Override 744 public long nextLong() { 745 long v = t; 746 t = f.applyAsLong(t); 747 return v; 748 } 749 }; 750 return StreamSupport.longStream(Spliterators.spliteratorUnknownSize( 751 iterator, 752 Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false); 753 } 754 755 /** 756 * Returns an infinite sequential unordered stream where each element is 757 * generated by the provided {@code LongSupplier}. This is suitable for 758 * generating constant streams, streams of random elements, etc. 759 * 760 * @param s the {@code LongSupplier} for generated elements 761 * @return a new infinite sequential unordered {@code LongStream} 762 */ generate(LongSupplier s)763 public static LongStream generate(LongSupplier s) { 764 Objects.requireNonNull(s); 765 return StreamSupport.longStream( 766 new StreamSpliterators.InfiniteSupplyingSpliterator.OfLong(Long.MAX_VALUE, s), false); 767 } 768 769 /** 770 * Returns a sequential ordered {@code LongStream} from {@code startInclusive} 771 * (inclusive) to {@code endExclusive} (exclusive) by an incremental step of 772 * {@code 1}. 773 * 774 * @apiNote 775 * <p>An equivalent sequence of increasing values can be produced 776 * sequentially using a {@code for} loop as follows: 777 * <pre>{@code 778 * for (long i = startInclusive; i < endExclusive ; i++) { ... } 779 * }</pre> 780 * 781 * @param startInclusive the (inclusive) initial value 782 * @param endExclusive the exclusive upper bound 783 * @return a sequential {@code LongStream} for the range of {@code long} 784 * elements 785 */ range(long startInclusive, final long endExclusive)786 public static LongStream range(long startInclusive, final long endExclusive) { 787 if (startInclusive >= endExclusive) { 788 return empty(); 789 } else if (endExclusive - startInclusive < 0) { 790 // Size of range > Long.MAX_VALUE 791 // Split the range in two and concatenate 792 // Note: if the range is [Long.MIN_VALUE, Long.MAX_VALUE) then 793 // the lower range, [Long.MIN_VALUE, 0) will be further split in two 794 // Android-changed: no divideUnsigned support yet, use BigInteger instead. 795 long m = startInclusive + 796 BigInteger.valueOf(endExclusive).subtract(BigInteger.valueOf(startInclusive)) 797 .divide(BigInteger.valueOf(2)).longValue() + 1; 798 799 return concat(range(startInclusive, m), range(m, endExclusive)); 800 } else { 801 return StreamSupport.longStream( 802 new Streams.RangeLongSpliterator(startInclusive, endExclusive, false), false); 803 } 804 } 805 806 /** 807 * Returns a sequential ordered {@code LongStream} from {@code startInclusive} 808 * (inclusive) to {@code endInclusive} (inclusive) by an incremental step of 809 * {@code 1}. 810 * 811 * @apiNote 812 * <p>An equivalent sequence of increasing values can be produced 813 * sequentially using a {@code for} loop as follows: 814 * <pre>{@code 815 * for (long i = startInclusive; i <= endInclusive ; i++) { ... } 816 * }</pre> 817 * 818 * @param startInclusive the (inclusive) initial value 819 * @param endInclusive the inclusive upper bound 820 * @return a sequential {@code LongStream} for the range of {@code long} 821 * elements 822 */ rangeClosed(long startInclusive, final long endInclusive)823 public static LongStream rangeClosed(long startInclusive, final long endInclusive) { 824 if (startInclusive > endInclusive) { 825 return empty(); 826 } else if (endInclusive - startInclusive + 1 <= 0) { 827 // Size of range > Long.MAX_VALUE 828 // Split the range in two and concatenate 829 // Note: if the range is [Long.MIN_VALUE, Long.MAX_VALUE] then 830 // the lower range, [Long.MIN_VALUE, 0), and upper range, 831 // [0, Long.MAX_VALUE], will both be further split in two 832 // Android-changed: no divideUnsigned support yet, use BigInteger instead. 833 long m = startInclusive + 834 BigInteger.valueOf(endInclusive).subtract(BigInteger.valueOf(startInclusive)) 835 .divide(BigInteger.valueOf(2)).longValue() + 1; 836 837 return concat(range(startInclusive, m), rangeClosed(m, endInclusive)); 838 } else { 839 return StreamSupport.longStream( 840 new Streams.RangeLongSpliterator(startInclusive, endInclusive, true), false); 841 } 842 } 843 844 /** 845 * Creates a lazily concatenated stream whose elements are all the 846 * elements of the first stream followed by all the elements of the 847 * second stream. The resulting stream is ordered if both 848 * of the input streams are ordered, and parallel if either of the input 849 * streams is parallel. When the resulting stream is closed, the close 850 * handlers for both input streams are invoked. 851 * 852 * @implNote 853 * Use caution when constructing streams from repeated concatenation. 854 * Accessing an element of a deeply concatenated stream can result in deep 855 * call chains, or even {@code StackOverflowException}. 856 * 857 * @param a the first stream 858 * @param b the second stream 859 * @return the concatenation of the two input streams 860 */ concat(LongStream a, LongStream b)861 public static LongStream concat(LongStream a, LongStream b) { 862 Objects.requireNonNull(a); 863 Objects.requireNonNull(b); 864 865 Spliterator.OfLong split = new Streams.ConcatSpliterator.OfLong( 866 a.spliterator(), b.spliterator()); 867 LongStream stream = StreamSupport.longStream(split, a.isParallel() || b.isParallel()); 868 return stream.onClose(Streams.composedClose(a, b)); 869 } 870 871 /** 872 * A mutable builder for a {@code LongStream}. 873 * 874 * <p>A stream builder has a lifecycle, which starts in a building 875 * phase, during which elements can be added, and then transitions to a built 876 * phase, after which elements may not be added. The built phase begins 877 * begins when the {@link #build()} method is called, which creates an 878 * ordered stream whose elements are the elements that were added to the 879 * stream builder, in the order they were added. 880 * 881 * @see LongStream#builder() 882 * @since 1.8 883 */ 884 public interface Builder extends LongConsumer { 885 886 /** 887 * Adds an element to the stream being built. 888 * 889 * @throws IllegalStateException if the builder has already transitioned 890 * to the built state 891 */ 892 @Override accept(long t)893 void accept(long t); 894 895 /** 896 * Adds an element to the stream being built. 897 * 898 * @implSpec 899 * The default implementation behaves as if: 900 * <pre>{@code 901 * accept(t) 902 * return this; 903 * }</pre> 904 * 905 * @param t the element to add 906 * @return {@code this} builder 907 * @throws IllegalStateException if the builder has already transitioned 908 * to the built state 909 */ add(long t)910 default Builder add(long t) { 911 accept(t); 912 return this; 913 } 914 915 /** 916 * Builds the stream, transitioning this builder to the built state. 917 * An {@code IllegalStateException} is thrown if there are further 918 * attempts to operate on the builder after it has entered the built 919 * state. 920 * 921 * @return the built stream 922 * @throws IllegalStateException if the builder has already transitioned 923 * to the built state 924 */ build()925 LongStream build(); 926 } 927 } 928