LongStream.java revision ff18b5f136f92154f2e05217e3953d10f459e561
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 */ 25package java.util.stream; 26 27import java.nio.charset.Charset; 28import java.util.Arrays; 29import java.util.Collection; 30import java.util.LongSummaryStatistics; 31import java.util.Objects; 32import java.util.OptionalDouble; 33import java.util.OptionalLong; 34import java.util.PrimitiveIterator; 35import java.util.Spliterator; 36import java.util.Spliterators; 37import java.util.concurrent.ConcurrentHashMap; 38import java.util.function.BiConsumer; 39import java.util.function.Function; 40import java.util.function.LongBinaryOperator; 41import java.util.function.LongConsumer; 42import java.util.function.LongFunction; 43import java.util.function.LongPredicate; 44import java.util.function.LongSupplier; 45import java.util.function.LongToDoubleFunction; 46import java.util.function.LongToIntFunction; 47import java.util.function.LongUnaryOperator; 48import java.util.function.ObjLongConsumer; 49import java.util.function.Supplier; 50 51/** 52 * A sequence of primitive long-valued elements supporting sequential and parallel 53 * aggregate operations. This is the {@code long} primitive specialization of 54 * {@link Stream}. 55 * 56 * <p>The following example illustrates an aggregate operation using 57 * {@link Stream} and {@link LongStream}, computing the sum of the weights of the 58 * red widgets: 59 * 60 * <pre>{@code 61 * long sum = widgets.stream() 62 * .filter(w -> w.getColor() == RED) 63 * .mapToLong(w -> w.getWeight()) 64 * .sum(); 65 * }</pre> 66 * 67 * See the class documentation for {@link Stream} and the package documentation 68 * for <a href="package-summary.html">java.util.stream</a> for additional 69 * specification of streams, stream operations, stream pipelines, and 70 * parallelism. 71 * 72 * @since 1.8 73 * @see Stream 74 * @see <a href="package-summary.html">java.util.stream</a> 75 */ 76public interface LongStream extends BaseStream<Long, LongStream> { 77 78 /** 79 * Returns a stream consisting of the elements of this stream that match 80 * the given predicate. 81 * 82 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 83 * operation</a>. 84 * 85 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 86 * <a href="package-summary.html#Statelessness">stateless</a> 87 * predicate to apply to each element to determine if it 88 * should be included 89 * @return the new stream 90 */ 91 LongStream filter(LongPredicate predicate); 92 93 /** 94 * Returns a stream consisting of the results of applying the given 95 * function to the elements of this stream. 96 * 97 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 98 * operation</a>. 99 * 100 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 101 * <a href="package-summary.html#Statelessness">stateless</a> 102 * function to apply to each element 103 * @return the new stream 104 */ 105 LongStream map(LongUnaryOperator mapper); 106 107 /** 108 * Returns an object-valued {@code Stream} consisting of the results of 109 * applying the given function to the elements of this stream. 110 * 111 * <p>This is an <a href="package-summary.html#StreamOps"> 112 * intermediate operation</a>. 113 * 114 * @param <U> the element type of the new stream 115 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 116 * <a href="package-summary.html#Statelessness">stateless</a> 117 * function to apply to each element 118 * @return the new stream 119 */ 120 <U> Stream<U> mapToObj(LongFunction<? extends U> mapper); 121 122 /** 123 * Returns an {@code IntStream} consisting of the results of applying the 124 * given function to the elements of this stream. 125 * 126 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 127 * operation</a>. 128 * 129 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 130 * <a href="package-summary.html#Statelessness">stateless</a> 131 * function to apply to each element 132 * @return the new stream 133 */ 134 IntStream mapToInt(LongToIntFunction mapper); 135 136 /** 137 * Returns a {@code DoubleStream} consisting of the results of applying the 138 * given function to the elements of this stream. 139 * 140 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 141 * operation</a>. 142 * 143 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 144 * <a href="package-summary.html#Statelessness">stateless</a> 145 * function to apply to each element 146 * @return the new stream 147 */ 148 DoubleStream mapToDouble(LongToDoubleFunction mapper); 149 150 /** 151 * Returns a stream consisting of the results of replacing each element of 152 * this stream with the contents of a mapped stream produced by applying 153 * the provided mapping function to each element. Each mapped stream is 154 * {@link java.util.stream.BaseStream#close() closed} after its contents 155 * have been placed into this stream. (If a mapped stream is {@code null} 156 * an empty stream is used, instead.) 157 * 158 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 159 * operation</a>. 160 * 161 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 162 * <a href="package-summary.html#Statelessness">stateless</a> 163 * function to apply to each element which produces a 164 * {@code LongStream} of new values 165 * @return the new stream 166 * @see Stream#flatMap(Function) 167 */ 168 LongStream flatMap(LongFunction<? extends LongStream> mapper); 169 170 /** 171 * Returns a stream consisting of the distinct elements of this stream. 172 * 173 * <p>This is a <a href="package-summary.html#StreamOps">stateful 174 * intermediate operation</a>. 175 * 176 * @return the new stream 177 */ 178 LongStream distinct(); 179 180 /** 181 * Returns a stream consisting of the elements of this stream in sorted 182 * order. 183 * 184 * <p>This is a <a href="package-summary.html#StreamOps">stateful 185 * intermediate operation</a>. 186 * 187 * @return the new stream 188 */ 189 LongStream sorted(); 190 191 /** 192 * Returns a stream consisting of the elements of this stream, additionally 193 * performing the provided action on each element as elements are consumed 194 * from the resulting stream. 195 * 196 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 197 * operation</a>. 198 * 199 * <p>For parallel stream pipelines, the action may be called at 200 * whatever time and in whatever thread the element is made available by the 201 * upstream operation. If the action modifies shared state, 202 * it is responsible for providing the required synchronization. 203 * 204 * @apiNote This method exists mainly to support debugging, where you want 205 * to see the elements as they flow past a certain point in a pipeline: 206 * <pre>{@code 207 * LongStream.of(1, 2, 3, 4) 208 * .filter(e -> e > 2) 209 * .peek(e -> System.out.println("Filtered value: " + e)) 210 * .map(e -> e * e) 211 * .peek(e -> System.out.println("Mapped value: " + e)) 212 * .sum(); 213 * }</pre> 214 * 215 * @param action a <a href="package-summary.html#NonInterference"> 216 * non-interfering</a> action to perform on the elements as 217 * they are consumed from the stream 218 * @return the new stream 219 */ 220 LongStream peek(LongConsumer action); 221 222 /** 223 * Returns a stream consisting of the elements of this stream, truncated 224 * to be no longer than {@code maxSize} in length. 225 * 226 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 227 * stateful intermediate operation</a>. 228 * 229 * @apiNote 230 * While {@code limit()} is generally a cheap operation on sequential 231 * stream pipelines, it can be quite expensive on ordered parallel pipelines, 232 * especially for large values of {@code maxSize}, since {@code limit(n)} 233 * is constrained to return not just any <em>n</em> elements, but the 234 * <em>first n</em> elements in the encounter order. Using an unordered 235 * stream source (such as {@link #generate(LongSupplier)}) or removing the 236 * ordering constraint with {@link #unordered()} may result in significant 237 * speedups of {@code limit()} in parallel pipelines, if the semantics of 238 * your situation permit. If consistency with encounter order is required, 239 * and you are experiencing poor performance or memory utilization with 240 * {@code limit()} in parallel pipelines, switching to sequential execution 241 * with {@link #sequential()} may improve performance. 242 * 243 * @param maxSize the number of elements the stream should be limited to 244 * @return the new stream 245 * @throws IllegalArgumentException if {@code maxSize} is negative 246 */ 247 LongStream limit(long maxSize); 248 249 /** 250 * Returns a stream consisting of the remaining elements of this stream 251 * after discarding the first {@code n} elements of the stream. 252 * If this stream contains fewer than {@code n} elements then an 253 * empty stream will be returned. 254 * 255 * <p>This is a <a href="package-summary.html#StreamOps">stateful 256 * intermediate operation</a>. 257 * 258 * @apiNote 259 * While {@code skip()} is generally a cheap operation on sequential 260 * stream pipelines, it can be quite expensive on ordered parallel pipelines, 261 * especially for large values of {@code n}, since {@code skip(n)} 262 * is constrained to skip not just any <em>n</em> elements, but the 263 * <em>first n</em> elements in the encounter order. Using an unordered 264 * stream source (such as {@link #generate(LongSupplier)}) or removing the 265 * ordering constraint with {@link #unordered()} may result in significant 266 * speedups of {@code skip()} in parallel pipelines, if the semantics of 267 * your situation permit. If consistency with encounter order is required, 268 * and you are experiencing poor performance or memory utilization with 269 * {@code skip()} in parallel pipelines, switching to sequential execution 270 * with {@link #sequential()} may improve performance. 271 * 272 * @param n the number of leading elements to skip 273 * @return the new stream 274 * @throws IllegalArgumentException if {@code n} is negative 275 */ 276 LongStream skip(long n); 277 278 /** 279 * Performs an action for each element of this stream. 280 * 281 * <p>This is a <a href="package-summary.html#StreamOps">terminal 282 * operation</a>. 283 * 284 * <p>For parallel stream pipelines, this operation does <em>not</em> 285 * guarantee to respect the encounter order of the stream, as doing so 286 * would sacrifice the benefit of parallelism. For any given element, the 287 * action may be performed at whatever time and in whatever thread the 288 * library chooses. If the action accesses shared state, it is 289 * responsible for providing the required synchronization. 290 * 291 * @param action a <a href="package-summary.html#NonInterference"> 292 * non-interfering</a> action to perform on the elements 293 */ 294 void forEach(LongConsumer action); 295 296 /** 297 * Performs an action for each element of this stream, guaranteeing that 298 * each element is processed in encounter order for streams that have a 299 * defined encounter order. 300 * 301 * <p>This is a <a href="package-summary.html#StreamOps">terminal 302 * operation</a>. 303 * 304 * @param action a <a href="package-summary.html#NonInterference"> 305 * non-interfering</a> action to perform on the elements 306 * @see #forEach(LongConsumer) 307 */ 308 void forEachOrdered(LongConsumer action); 309 310 /** 311 * Returns an array containing the elements of this stream. 312 * 313 * <p>This is a <a href="package-summary.html#StreamOps">terminal 314 * operation</a>. 315 * 316 * @return an array containing the elements of this stream 317 */ 318 long[] toArray(); 319 320 /** 321 * Performs a <a href="package-summary.html#Reduction">reduction</a> on the 322 * elements of this stream, using the provided identity value and an 323 * <a href="package-summary.html#Associativity">associative</a> 324 * accumulation function, and returns the reduced value. This is equivalent 325 * to: 326 * <pre>{@code 327 * long result = identity; 328 * for (long element : this stream) 329 * result = accumulator.applyAsLong(result, element) 330 * return result; 331 * }</pre> 332 * 333 * but is not constrained to execute sequentially. 334 * 335 * <p>The {@code identity} value must be an identity for the accumulator 336 * function. This means that for all {@code x}, 337 * {@code accumulator.apply(identity, x)} is equal to {@code x}. 338 * The {@code accumulator} function must be an 339 * <a href="package-summary.html#Associativity">associative</a> function. 340 * 341 * <p>This is a <a href="package-summary.html#StreamOps">terminal 342 * operation</a>. 343 * 344 * @apiNote Sum, min, max, and average are all special cases of reduction. 345 * Summing a stream of numbers can be expressed as: 346 * 347 * <pre>{@code 348 * long sum = integers.reduce(0, (a, b) -> a+b); 349 * }</pre> 350 * 351 * or more compactly: 352 * 353 * <pre>{@code 354 * long sum = integers.reduce(0, Long::sum); 355 * }</pre> 356 * 357 * <p>While this may seem a more roundabout way to perform an aggregation 358 * compared to simply mutating a running total in a loop, reduction 359 * operations parallelize more gracefully, without needing additional 360 * synchronization and with greatly reduced risk of data races. 361 * 362 * @param identity the identity value for the accumulating function 363 * @param op an <a href="package-summary.html#Associativity">associative</a>, 364 * <a href="package-summary.html#NonInterference">non-interfering</a>, 365 * <a href="package-summary.html#Statelessness">stateless</a> 366 * function for combining two values 367 * @return the result of the reduction 368 * @see #sum() 369 * @see #min() 370 * @see #max() 371 * @see #average() 372 */ 373 long reduce(long identity, LongBinaryOperator op); 374 375 /** 376 * Performs a <a href="package-summary.html#Reduction">reduction</a> on the 377 * elements of this stream, using an 378 * <a href="package-summary.html#Associativity">associative</a> accumulation 379 * function, and returns an {@code OptionalLong} describing the reduced value, 380 * if any. This is equivalent to: 381 * <pre>{@code 382 * boolean foundAny = false; 383 * long result = null; 384 * for (long element : this stream) { 385 * if (!foundAny) { 386 * foundAny = true; 387 * result = element; 388 * } 389 * else 390 * result = accumulator.applyAsLong(result, element); 391 * } 392 * return foundAny ? OptionalLong.of(result) : OptionalLong.empty(); 393 * }</pre> 394 * 395 * but is not constrained to execute sequentially. 396 * 397 * <p>The {@code accumulator} function must be an 398 * <a href="package-summary.html#Associativity">associative</a> function. 399 * 400 * <p>This is a <a href="package-summary.html#StreamOps">terminal 401 * operation</a>. 402 * 403 * @param op an <a href="package-summary.html#Associativity">associative</a>, 404 * <a href="package-summary.html#NonInterference">non-interfering</a>, 405 * <a href="package-summary.html#Statelessness">stateless</a> 406 * function for combining two values 407 * @return the result of the reduction 408 * @see #reduce(long, LongBinaryOperator) 409 */ 410 OptionalLong reduce(LongBinaryOperator op); 411 412 /** 413 * Performs a <a href="package-summary.html#MutableReduction">mutable 414 * reduction</a> operation on the elements of this stream. A mutable 415 * reduction is one in which the reduced value is a mutable result container, 416 * such as an {@code ArrayList}, and elements are incorporated by updating 417 * the state of the result rather than by replacing the result. This 418 * produces a result equivalent to: 419 * <pre>{@code 420 * R result = supplier.get(); 421 * for (long element : this stream) 422 * accumulator.accept(result, element); 423 * return result; 424 * }</pre> 425 * 426 * <p>Like {@link #reduce(long, LongBinaryOperator)}, {@code collect} operations 427 * can be parallelized without requiring additional synchronization. 428 * 429 * <p>This is a <a href="package-summary.html#StreamOps">terminal 430 * operation</a>. 431 * 432 * @param <R> type of the result 433 * @param supplier a function that creates a new result container. For a 434 * parallel execution, this function may be called 435 * multiple times and must return a fresh value each time. 436 * @param accumulator an <a href="package-summary.html#Associativity">associative</a>, 437 * <a href="package-summary.html#NonInterference">non-interfering</a>, 438 * <a href="package-summary.html#Statelessness">stateless</a> 439 * function for incorporating an additional element into a result 440 * @param combiner an <a href="package-summary.html#Associativity">associative</a>, 441 * <a href="package-summary.html#NonInterference">non-interfering</a>, 442 * <a href="package-summary.html#Statelessness">stateless</a> 443 * function for combining two values, which must be 444 * compatible with the accumulator function 445 * @return the result of the reduction 446 * @see Stream#collect(Supplier, BiConsumer, BiConsumer) 447 */ 448 <R> R collect(Supplier<R> supplier, 449 ObjLongConsumer<R> accumulator, 450 BiConsumer<R, R> combiner); 451 452 /** 453 * Returns the sum of elements in this stream. This is a special case 454 * of a <a href="package-summary.html#Reduction">reduction</a> 455 * and is equivalent to: 456 * <pre>{@code 457 * return reduce(0, Long::sum); 458 * }</pre> 459 * 460 * <p>This is a <a href="package-summary.html#StreamOps">terminal 461 * operation</a>. 462 * 463 * @return the sum of elements in this stream 464 */ 465 long sum(); 466 467 /** 468 * Returns an {@code OptionalLong} describing the minimum element of this 469 * stream, or an empty optional if this stream is empty. This is a special 470 * case of a <a href="package-summary.html#Reduction">reduction</a> 471 * and is equivalent to: 472 * <pre>{@code 473 * return reduce(Long::min); 474 * }</pre> 475 * 476 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. 477 * 478 * @return an {@code OptionalLong} containing the minimum element of this 479 * stream, or an empty {@code OptionalLong} if the stream is empty 480 */ 481 OptionalLong min(); 482 483 /** 484 * Returns an {@code OptionalLong} describing the maximum element of this 485 * stream, or an empty optional if this stream is empty. This is a special 486 * case of a <a href="package-summary.html#Reduction">reduction</a> 487 * and is equivalent to: 488 * <pre>{@code 489 * return reduce(Long::max); 490 * }</pre> 491 * 492 * <p>This is a <a href="package-summary.html#StreamOps">terminal 493 * operation</a>. 494 * 495 * @return an {@code OptionalLong} containing the maximum element of this 496 * stream, or an empty {@code OptionalLong} if the stream is empty 497 */ 498 OptionalLong max(); 499 500 /** 501 * Returns the count of elements in this stream. This is a special case of 502 * a <a href="package-summary.html#Reduction">reduction</a> and is 503 * equivalent to: 504 * <pre>{@code 505 * return map(e -> 1L).sum(); 506 * }</pre> 507 * 508 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. 509 * 510 * @return the count of elements in this stream 511 */ 512 long count(); 513 514 /** 515 * Returns an {@code OptionalDouble} describing the arithmetic mean of elements of 516 * this stream, or an empty optional if this stream is empty. This is a 517 * special case of a 518 * <a href="package-summary.html#Reduction">reduction</a>. 519 * 520 * <p>This is a <a href="package-summary.html#StreamOps">terminal 521 * operation</a>. 522 * 523 * @return an {@code OptionalDouble} containing the average element of this 524 * stream, or an empty optional if the stream is empty 525 */ 526 OptionalDouble average(); 527 528 /** 529 * Returns a {@code LongSummaryStatistics} describing various summary data 530 * about the elements of this stream. This is a special case of a 531 * <a href="package-summary.html#Reduction">reduction</a>. 532 * 533 * <p>This is a <a href="package-summary.html#StreamOps">terminal 534 * operation</a>. 535 * 536 * @return a {@code LongSummaryStatistics} describing various summary data 537 * about the elements of this stream 538 */ 539 LongSummaryStatistics summaryStatistics(); 540 541 /** 542 * Returns whether any elements of this stream match the provided 543 * predicate. May not evaluate the predicate on all elements if not 544 * necessary for determining the result. If the stream is empty then 545 * {@code false} is returned and the predicate is not evaluated. 546 * 547 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 548 * terminal operation</a>. 549 * 550 * @apiNote 551 * This method evaluates the <em>existential quantification</em> of the 552 * predicate over the elements of the stream (for some x P(x)). 553 * 554 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 555 * <a href="package-summary.html#Statelessness">stateless</a> 556 * predicate to apply to elements of this stream 557 * @return {@code true} if any elements of the stream match the provided 558 * predicate, otherwise {@code false} 559 */ 560 boolean anyMatch(LongPredicate predicate); 561 562 /** 563 * Returns whether all elements of this stream match the provided predicate. 564 * May not evaluate the predicate on all elements if not necessary for 565 * determining the result. If the stream is empty then {@code true} is 566 * returned and the predicate is not evaluated. 567 * 568 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 569 * terminal operation</a>. 570 * 571 * @apiNote 572 * This method evaluates the <em>universal quantification</em> of the 573 * predicate over the elements of the stream (for all x P(x)). If the 574 * stream is empty, the quantification is said to be <em>vacuously 575 * satisfied</em> and is always {@code true} (regardless of P(x)). 576 * 577 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 578 * <a href="package-summary.html#Statelessness">stateless</a> 579 * predicate to apply to elements of this stream 580 * @return {@code true} if either all elements of the stream match the 581 * provided predicate or the stream is empty, otherwise {@code false} 582 */ 583 boolean allMatch(LongPredicate predicate); 584 585 /** 586 * Returns whether no elements of this stream match the provided predicate. 587 * May not evaluate the predicate on all elements if not necessary for 588 * determining the result. If the stream is empty then {@code true} is 589 * returned and the predicate is not evaluated. 590 * 591 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 592 * terminal operation</a>. 593 * 594 * @apiNote 595 * This method evaluates the <em>universal quantification</em> of the 596 * negated predicate over the elements of the stream (for all x ~P(x)). If 597 * the stream is empty, the quantification is said to be vacuously satisfied 598 * and is always {@code true}, regardless of P(x). 599 * 600 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 601 * <a href="package-summary.html#Statelessness">stateless</a> 602 * predicate to apply to elements of this stream 603 * @return {@code true} if either no elements of the stream match the 604 * provided predicate or the stream is empty, otherwise {@code false} 605 */ 606 boolean noneMatch(LongPredicate predicate); 607 608 /** 609 * Returns an {@link OptionalLong} describing the first element of this 610 * stream, or an empty {@code OptionalLong} if the stream is empty. If the 611 * stream has no encounter order, then any element may be returned. 612 * 613 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 614 * terminal operation</a>. 615 * 616 * @return an {@code OptionalLong} describing the first element of this 617 * stream, or an empty {@code OptionalLong} if the stream is empty 618 */ 619 OptionalLong findFirst(); 620 621 /** 622 * Returns an {@link OptionalLong} describing some element of the stream, or 623 * an empty {@code OptionalLong} if the stream is empty. 624 * 625 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 626 * terminal operation</a>. 627 * 628 * <p>The behavior of this operation is explicitly nondeterministic; it is 629 * free to select any element in the stream. This is to allow for maximal 630 * performance in parallel operations; the cost is that multiple invocations 631 * on the same source may not return the same result. (If a stable result 632 * is desired, use {@link #findFirst()} instead.) 633 * 634 * @return an {@code OptionalLong} describing some element of this stream, 635 * or an empty {@code OptionalLong} if the stream is empty 636 * @see #findFirst() 637 */ 638 OptionalLong findAny(); 639 640 /** 641 * Returns a {@code DoubleStream} consisting of the elements of this stream, 642 * converted to {@code double}. 643 * 644 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 645 * operation</a>. 646 * 647 * @return a {@code DoubleStream} consisting of the elements of this stream, 648 * converted to {@code double} 649 */ 650 DoubleStream asDoubleStream(); 651 652 /** 653 * Returns a {@code Stream} consisting of the elements of this stream, 654 * each boxed to a {@code Long}. 655 * 656 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 657 * operation</a>. 658 * 659 * @return a {@code Stream} consistent of the elements of this stream, 660 * each boxed to {@code Long} 661 */ 662 Stream<Long> boxed(); 663 664 @Override 665 LongStream sequential(); 666 667 @Override 668 LongStream parallel(); 669 670 @Override 671 PrimitiveIterator.OfLong iterator(); 672 673 @Override 674 Spliterator.OfLong spliterator(); 675 676 // Static factories 677 678 /** 679 * Returns a builder for a {@code LongStream}. 680 * 681 * @return a stream builder 682 */ 683 public static Builder builder() { 684 return new Streams.LongStreamBuilderImpl(); 685 } 686 687 /** 688 * Returns an empty sequential {@code LongStream}. 689 * 690 * @return an empty sequential stream 691 */ 692 public static LongStream empty() { 693 return StreamSupport.longStream(Spliterators.emptyLongSpliterator(), false); 694 } 695 696 /** 697 * Returns a sequential {@code LongStream} containing a single element. 698 * 699 * @param t the single element 700 * @return a singleton sequential stream 701 */ 702 public static LongStream of(long t) { 703 return StreamSupport.longStream(new Streams.LongStreamBuilderImpl(t), false); 704 } 705 706 /** 707 * Returns a sequential ordered stream whose elements are the specified values. 708 * 709 * @param values the elements of the new stream 710 * @return the new stream 711 */ 712 public static LongStream of(long... values) { 713 return Arrays.stream(values); 714 } 715 716 /** 717 * Returns an infinite sequential ordered {@code LongStream} produced by iterative 718 * application of a function {@code f} to an initial element {@code seed}, 719 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)}, 720 * {@code f(f(seed))}, etc. 721 * 722 * <p>The first element (position {@code 0}) in the {@code LongStream} will 723 * be the provided {@code seed}. For {@code n > 0}, the element at position 724 * {@code n}, will be the result of applying the function {@code f} to the 725 * element at position {@code n - 1}. 726 * 727 * @param seed the initial element 728 * @param f a function to be applied to to the previous element to produce 729 * a new element 730 * @return a new sequential {@code LongStream} 731 */ 732 public static LongStream iterate(final long seed, final LongUnaryOperator f) { 733 Objects.requireNonNull(f); 734 final PrimitiveIterator.OfLong iterator = new PrimitiveIterator.OfLong() { 735 long t = seed; 736 737 @Override 738 public boolean hasNext() { 739 return true; 740 } 741 742 @Override 743 public long nextLong() { 744 long v = t; 745 t = f.applyAsLong(t); 746 return v; 747 } 748 }; 749 return StreamSupport.longStream(Spliterators.spliteratorUnknownSize( 750 iterator, 751 Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false); 752 } 753 754 /** 755 * Returns an infinite sequential unordered stream where each element is 756 * generated by the provided {@code LongSupplier}. This is suitable for 757 * generating constant streams, streams of random elements, etc. 758 * 759 * @param s the {@code LongSupplier} for generated elements 760 * @return a new infinite sequential unordered {@code LongStream} 761 */ 762 public static LongStream generate(LongSupplier s) { 763 Objects.requireNonNull(s); 764 return StreamSupport.longStream( 765 new StreamSpliterators.InfiniteSupplyingSpliterator.OfLong(Long.MAX_VALUE, s), false); 766 } 767 768 /** 769 * Returns a sequential ordered {@code LongStream} from {@code startInclusive} 770 * (inclusive) to {@code endExclusive} (exclusive) by an incremental step of 771 * {@code 1}. 772 * 773 * @apiNote 774 * <p>An equivalent sequence of increasing values can be produced 775 * sequentially using a {@code for} loop as follows: 776 * <pre>{@code 777 * for (long i = startInclusive; i < endExclusive ; i++) { ... } 778 * }</pre> 779 * 780 * @param startInclusive the (inclusive) initial value 781 * @param endExclusive the exclusive upper bound 782 * @return a sequential {@code LongStream} for the range of {@code long} 783 * elements 784 */ 785 public static LongStream range(long startInclusive, final long endExclusive) { 786 if (startInclusive >= endExclusive) { 787 return empty(); 788 } else if (endExclusive - startInclusive < 0) { 789 // Size of range > Long.MAX_VALUE 790 // Split the range in two and concatenate 791 // Note: if the range is [Long.MIN_VALUE, Long.MAX_VALUE) then 792 // the lower range, [Long.MIN_VALUE, 0) will be further split in two 793 // Android-changed: no divideUnsigned support yet 794 long m = startInclusive + ((endExclusive - startInclusive) / 2) + 1; 795 return concat(range(startInclusive, m), range(m, endExclusive)); 796 } else { 797 return StreamSupport.longStream( 798 new Streams.RangeLongSpliterator(startInclusive, endExclusive, false), false); 799 } 800 } 801 802 /** 803 * Returns a sequential ordered {@code LongStream} from {@code startInclusive} 804 * (inclusive) to {@code endInclusive} (inclusive) by an incremental step of 805 * {@code 1}. 806 * 807 * @apiNote 808 * <p>An equivalent sequence of increasing values can be produced 809 * sequentially using a {@code for} loop as follows: 810 * <pre>{@code 811 * for (long i = startInclusive; i <= endInclusive ; i++) { ... } 812 * }</pre> 813 * 814 * @param startInclusive the (inclusive) initial value 815 * @param endInclusive the inclusive upper bound 816 * @return a sequential {@code LongStream} for the range of {@code long} 817 * elements 818 */ 819 public static LongStream rangeClosed(long startInclusive, final long endInclusive) { 820 if (startInclusive > endInclusive) { 821 return empty(); 822 } else if (endInclusive - startInclusive + 1 <= 0) { 823 // Size of range > Long.MAX_VALUE 824 // Split the range in two and concatenate 825 // Note: if the range is [Long.MIN_VALUE, Long.MAX_VALUE] then 826 // the lower range, [Long.MIN_VALUE, 0), and upper range, 827 // [0, Long.MAX_VALUE], will both be further split in two 828 // Android-changed: no divideUnsigned support yet 829 long m = startInclusive + ((endInclusive - startInclusive) / 2) + 1; 830 return concat(range(startInclusive, m), rangeClosed(m, endInclusive)); 831 } else { 832 return StreamSupport.longStream( 833 new Streams.RangeLongSpliterator(startInclusive, endInclusive, true), false); 834 } 835 } 836 837 /** 838 * Creates a lazily concatenated stream whose elements are all the 839 * elements of the first stream followed by all the elements of the 840 * second stream. The resulting stream is ordered if both 841 * of the input streams are ordered, and parallel if either of the input 842 * streams is parallel. When the resulting stream is closed, the close 843 * handlers for both input streams are invoked. 844 * 845 * @implNote 846 * Use caution when constructing streams from repeated concatenation. 847 * Accessing an element of a deeply concatenated stream can result in deep 848 * call chains, or even {@code StackOverflowException}. 849 * 850 * @param a the first stream 851 * @param b the second stream 852 * @return the concatenation of the two input streams 853 */ 854 public static LongStream concat(LongStream a, LongStream b) { 855 Objects.requireNonNull(a); 856 Objects.requireNonNull(b); 857 858 Spliterator.OfLong split = new Streams.ConcatSpliterator.OfLong( 859 a.spliterator(), b.spliterator()); 860 LongStream stream = StreamSupport.longStream(split, a.isParallel() || b.isParallel()); 861 return stream.onClose(Streams.composedClose(a, b)); 862 } 863 864 /** 865 * A mutable builder for a {@code LongStream}. 866 * 867 * <p>A stream builder has a lifecycle, which starts in a building 868 * phase, during which elements can be added, and then transitions to a built 869 * phase, after which elements may not be added. The built phase begins 870 * begins when the {@link #build()} method is called, which creates an 871 * ordered stream whose elements are the elements that were added to the 872 * stream builder, in the order they were added. 873 * 874 * @see LongStream#builder() 875 * @since 1.8 876 */ 877 public interface Builder extends LongConsumer { 878 879 /** 880 * Adds an element to the stream being built. 881 * 882 * @throws IllegalStateException if the builder has already transitioned 883 * to the built state 884 */ 885 @Override 886 void accept(long t); 887 888 /** 889 * Adds an element to the stream being built. 890 * 891 * @implSpec 892 * The default implementation behaves as if: 893 * <pre>{@code 894 * accept(t) 895 * return this; 896 * }</pre> 897 * 898 * @param t the element to add 899 * @return {@code this} builder 900 * @throws IllegalStateException if the builder has already transitioned 901 * to the built state 902 */ 903 default Builder add(long t) { 904 accept(t); 905 return this; 906 } 907 908 /** 909 * Builds the stream, transitioning this builder to the built state. 910 * An {@code IllegalStateException} is thrown if there are further 911 * attempts to operate on the builder after it has entered the built 912 * state. 913 * 914 * @return the built stream 915 * @throws IllegalStateException if the builder has already transitioned 916 * to the built state 917 */ 918 LongStream build(); 919 } 920} 921