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