1 /* 2 * Copyright (c) 2012, 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.util.Arrays; 28 import java.util.IntSummaryStatistics; 29 import java.util.Objects; 30 import java.util.OptionalDouble; 31 import java.util.OptionalInt; 32 import java.util.PrimitiveIterator; 33 import java.util.Spliterator; 34 import java.util.Spliterators; 35 import java.util.function.BiConsumer; 36 import java.util.function.Function; 37 import java.util.function.IntBinaryOperator; 38 import java.util.function.IntConsumer; 39 import java.util.function.IntFunction; 40 import java.util.function.IntPredicate; 41 import java.util.function.IntSupplier; 42 import java.util.function.IntToDoubleFunction; 43 import java.util.function.IntToLongFunction; 44 import java.util.function.IntUnaryOperator; 45 import java.util.function.ObjIntConsumer; 46 import java.util.function.Supplier; 47 48 /** 49 * A sequence of primitive int-valued elements supporting sequential and parallel 50 * aggregate operations. This is the {@code int} primitive specialization of 51 * {@link Stream}. 52 * 53 * <p>The following example illustrates an aggregate operation using 54 * {@link Stream} and {@link IntStream}, computing the sum of the weights of the 55 * red widgets: 56 * 57 * <pre>{@code 58 * int sum = widgets.stream() 59 * .filter(w -> w.getColor() == RED) 60 * .mapToInt(w -> w.getWeight()) 61 * .sum(); 62 * }</pre> 63 * 64 * See the class documentation for {@link Stream} and the package documentation 65 * for <a href="package-summary.html">java.util.stream</a> for additional 66 * specification of streams, stream operations, stream pipelines, and 67 * parallelism. 68 * 69 * @since 1.8 70 * @see Stream 71 * @see <a href="package-summary.html">java.util.stream</a> 72 */ 73 public interface IntStream extends BaseStream<Integer, IntStream> { 74 75 /** 76 * Returns a stream consisting of the elements of this stream that match 77 * the given predicate. 78 * 79 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 80 * operation</a>. 81 * 82 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 83 * <a href="package-summary.html#Statelessness">stateless</a> 84 * predicate to apply to each element to determine if it 85 * should be included 86 * @return the new stream 87 */ filter(IntPredicate predicate)88 IntStream filter(IntPredicate predicate); 89 90 /** 91 * Returns a stream consisting of the results of applying the given 92 * function to the elements of this stream. 93 * 94 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 95 * operation</a>. 96 * 97 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 98 * <a href="package-summary.html#Statelessness">stateless</a> 99 * function to apply to each element 100 * @return the new stream 101 */ map(IntUnaryOperator mapper)102 IntStream map(IntUnaryOperator mapper); 103 104 /** 105 * Returns an object-valued {@code Stream} consisting of the results of 106 * applying the given function to the elements of this stream. 107 * 108 * <p>This is an <a href="package-summary.html#StreamOps"> 109 * intermediate operation</a>. 110 * 111 * @param <U> the element type of the new stream 112 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 113 * <a href="package-summary.html#Statelessness">stateless</a> 114 * function to apply to each element 115 * @return the new stream 116 */ mapToObj(IntFunction<? extends U> mapper)117 <U> Stream<U> mapToObj(IntFunction<? extends U> mapper); 118 119 /** 120 * Returns a {@code LongStream} consisting of the results of applying the 121 * given function to the elements of this stream. 122 * 123 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 124 * operation</a>. 125 * 126 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 127 * <a href="package-summary.html#Statelessness">stateless</a> 128 * function to apply to each element 129 * @return the new stream 130 */ mapToLong(IntToLongFunction mapper)131 LongStream mapToLong(IntToLongFunction mapper); 132 133 /** 134 * Returns a {@code DoubleStream} consisting of the results of applying the 135 * given function to the elements of this stream. 136 * 137 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 138 * operation</a>. 139 * 140 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 141 * <a href="package-summary.html#Statelessness">stateless</a> 142 * function to apply to each element 143 * @return the new stream 144 */ mapToDouble(IntToDoubleFunction mapper)145 DoubleStream mapToDouble(IntToDoubleFunction mapper); 146 147 /** 148 * Returns a stream consisting of the results of replacing each element of 149 * this stream with the contents of a mapped stream produced by applying 150 * the provided mapping function to each element. Each mapped stream is 151 * {@link java.util.stream.BaseStream#close() closed} after its contents 152 * have been placed into this stream. (If a mapped stream is {@code null} 153 * an empty stream is used, instead.) 154 * 155 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 156 * operation</a>. 157 * 158 * @param mapper a <a href="package-summary.html#NonInterference">non-interfering</a>, 159 * <a href="package-summary.html#Statelessness">stateless</a> 160 * function to apply to each element which produces an 161 * {@code IntStream} of new values 162 * @return the new stream 163 * @see Stream#flatMap(Function) 164 */ flatMap(IntFunction<? extends IntStream> mapper)165 IntStream flatMap(IntFunction<? extends IntStream> mapper); 166 167 /** 168 * Returns a stream consisting of the distinct elements of this stream. 169 * 170 * <p>This is a <a href="package-summary.html#StreamOps">stateful 171 * intermediate operation</a>. 172 * 173 * @return the new stream 174 */ distinct()175 IntStream distinct(); 176 177 /** 178 * Returns a stream consisting of the elements of this stream in sorted 179 * order. 180 * 181 * <p>This is a <a href="package-summary.html#StreamOps">stateful 182 * intermediate operation</a>. 183 * 184 * @return the new stream 185 */ sorted()186 IntStream sorted(); 187 188 /** 189 * Returns a stream consisting of the elements of this stream, additionally 190 * performing the provided action on each element as elements are consumed 191 * from the resulting stream. 192 * 193 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 194 * operation</a>. 195 * 196 * <p>For parallel stream pipelines, the action may be called at 197 * whatever time and in whatever thread the element is made available by the 198 * upstream operation. If the action modifies shared state, 199 * it is responsible for providing the required synchronization. 200 * 201 * @apiNote This method exists mainly to support debugging, where you want 202 * to see the elements as they flow past a certain point in a pipeline: 203 * <pre>{@code 204 * IntStream.of(1, 2, 3, 4) 205 * .filter(e -> e > 2) 206 * .peek(e -> System.out.println("Filtered value: " + e)) 207 * .map(e -> e * e) 208 * .peek(e -> System.out.println("Mapped value: " + e)) 209 * .sum(); 210 * }</pre> 211 * 212 * @param action a <a href="package-summary.html#NonInterference"> 213 * non-interfering</a> action to perform on the elements as 214 * they are consumed from the stream 215 * @return the new stream 216 */ peek(IntConsumer action)217 IntStream peek(IntConsumer action); 218 219 /** 220 * Returns a stream consisting of the elements of this stream, truncated 221 * to be no longer than {@code maxSize} in length. 222 * 223 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 224 * stateful intermediate operation</a>. 225 * 226 * @apiNote 227 * While {@code limit()} is generally a cheap operation on sequential 228 * stream pipelines, it can be quite expensive on ordered parallel pipelines, 229 * especially for large values of {@code maxSize}, since {@code limit(n)} 230 * is constrained to return not just any <em>n</em> elements, but the 231 * <em>first n</em> elements in the encounter order. Using an unordered 232 * stream source (such as {@link #generate(IntSupplier)}) or removing the 233 * ordering constraint with {@link #unordered()} may result in significant 234 * speedups of {@code limit()} in parallel pipelines, if the semantics of 235 * your situation permit. If consistency with encounter order is required, 236 * and you are experiencing poor performance or memory utilization with 237 * {@code limit()} in parallel pipelines, switching to sequential execution 238 * with {@link #sequential()} may improve performance. 239 * 240 * @param maxSize the number of elements the stream should be limited to 241 * @return the new stream 242 * @throws IllegalArgumentException if {@code maxSize} is negative 243 */ limit(long maxSize)244 IntStream limit(long maxSize); 245 246 /** 247 * Returns a stream consisting of the remaining elements of this stream 248 * after discarding the first {@code n} elements of the stream. 249 * If this stream contains fewer than {@code n} elements then an 250 * empty stream will be returned. 251 * 252 * <p>This is a <a href="package-summary.html#StreamOps">stateful 253 * intermediate operation</a>. 254 * 255 * @apiNote 256 * While {@code skip()} is generally a cheap operation on sequential 257 * stream pipelines, it can be quite expensive on ordered parallel pipelines, 258 * especially for large values of {@code n}, since {@code skip(n)} 259 * is constrained to skip not just any <em>n</em> elements, but the 260 * <em>first n</em> elements in the encounter order. Using an unordered 261 * stream source (such as {@link #generate(IntSupplier)}) or removing the 262 * ordering constraint with {@link #unordered()} may result in significant 263 * speedups of {@code skip()} in parallel pipelines, if the semantics of 264 * your situation permit. If consistency with encounter order is required, 265 * and you are experiencing poor performance or memory utilization with 266 * {@code skip()} in parallel pipelines, switching to sequential execution 267 * with {@link #sequential()} may improve performance. 268 * 269 * @param n the number of leading elements to skip 270 * @return the new stream 271 * @throws IllegalArgumentException if {@code n} is negative 272 */ skip(long n)273 IntStream skip(long n); 274 275 /** 276 * Performs an action for each element of this stream. 277 * 278 * <p>This is a <a href="package-summary.html#StreamOps">terminal 279 * operation</a>. 280 * 281 * <p>For parallel stream pipelines, this operation does <em>not</em> 282 * guarantee to respect the encounter order of the stream, as doing so 283 * would sacrifice the benefit of parallelism. For any given element, the 284 * action may be performed at whatever time and in whatever thread the 285 * library chooses. If the action accesses shared state, it is 286 * responsible for providing the required synchronization. 287 * 288 * @param action a <a href="package-summary.html#NonInterference"> 289 * non-interfering</a> action to perform on the elements 290 */ forEach(IntConsumer action)291 void forEach(IntConsumer action); 292 293 /** 294 * Performs an action for each element of this stream, guaranteeing that 295 * each element is processed in encounter order for streams that have a 296 * defined encounter order. 297 * 298 * <p>This is a <a href="package-summary.html#StreamOps">terminal 299 * operation</a>. 300 * 301 * @param action a <a href="package-summary.html#NonInterference"> 302 * non-interfering</a> action to perform on the elements 303 * @see #forEach(IntConsumer) 304 */ forEachOrdered(IntConsumer action)305 void forEachOrdered(IntConsumer action); 306 307 /** 308 * Returns an array containing the elements of this stream. 309 * 310 * <p>This is a <a href="package-summary.html#StreamOps">terminal 311 * operation</a>. 312 * 313 * @return an array containing the elements of this stream 314 */ toArray()315 int[] toArray(); 316 317 /** 318 * Performs a <a href="package-summary.html#Reduction">reduction</a> on the 319 * elements of this stream, using the provided identity value and an 320 * <a href="package-summary.html#Associativity">associative</a> 321 * accumulation function, and returns the reduced value. This is equivalent 322 * to: 323 * <pre>{@code 324 * int result = identity; 325 * for (int element : this stream) 326 * result = accumulator.applyAsInt(result, element) 327 * return result; 328 * }</pre> 329 * 330 * but is not constrained to execute sequentially. 331 * 332 * <p>The {@code identity} value must be an identity for the accumulator 333 * function. This means that for all {@code x}, 334 * {@code accumulator.apply(identity, x)} is equal to {@code x}. 335 * The {@code accumulator} function must be an 336 * <a href="package-summary.html#Associativity">associative</a> function. 337 * 338 * <p>This is a <a href="package-summary.html#StreamOps">terminal 339 * operation</a>. 340 * 341 * @apiNote Sum, min, max, and average are all special cases of reduction. 342 * Summing a stream of numbers can be expressed as: 343 * 344 * <pre>{@code 345 * int sum = integers.reduce(0, (a, b) -> a+b); 346 * }</pre> 347 * 348 * or more compactly: 349 * 350 * <pre>{@code 351 * int sum = integers.reduce(0, Integer::sum); 352 * }</pre> 353 * 354 * <p>While this may seem a more roundabout way to perform an aggregation 355 * compared to simply mutating a running total in a loop, reduction 356 * operations parallelize more gracefully, without needing additional 357 * synchronization and with greatly reduced risk of data races. 358 * 359 * @param identity the identity value for the accumulating function 360 * @param op an <a href="package-summary.html#Associativity">associative</a>, 361 * <a href="package-summary.html#NonInterference">non-interfering</a>, 362 * <a href="package-summary.html#Statelessness">stateless</a> 363 * function for combining two values 364 * @return the result of the reduction 365 * @see #sum() 366 * @see #min() 367 * @see #max() 368 * @see #average() 369 */ reduce(int identity, IntBinaryOperator op)370 int reduce(int identity, IntBinaryOperator op); 371 372 /** 373 * Performs a <a href="package-summary.html#Reduction">reduction</a> on the 374 * elements of this stream, using an 375 * <a href="package-summary.html#Associativity">associative</a> accumulation 376 * function, and returns an {@code OptionalInt} describing the reduced value, 377 * if any. This is equivalent to: 378 * <pre>{@code 379 * boolean foundAny = false; 380 * int result = null; 381 * for (int element : this stream) { 382 * if (!foundAny) { 383 * foundAny = true; 384 * result = element; 385 * } 386 * else 387 * result = accumulator.applyAsInt(result, element); 388 * } 389 * return foundAny ? OptionalInt.of(result) : OptionalInt.empty(); 390 * }</pre> 391 * 392 * but is not constrained to execute sequentially. 393 * 394 * <p>The {@code accumulator} function must be an 395 * <a href="package-summary.html#Associativity">associative</a> function. 396 * 397 * <p>This is a <a href="package-summary.html#StreamOps">terminal 398 * operation</a>. 399 * 400 * @param op an <a href="package-summary.html#Associativity">associative</a>, 401 * <a href="package-summary.html#NonInterference">non-interfering</a>, 402 * <a href="package-summary.html#Statelessness">stateless</a> 403 * function for combining two values 404 * @return the result of the reduction 405 * @see #reduce(int, IntBinaryOperator) 406 */ reduce(IntBinaryOperator op)407 OptionalInt reduce(IntBinaryOperator op); 408 409 /** 410 * Performs a <a href="package-summary.html#MutableReduction">mutable 411 * reduction</a> operation on the elements of this stream. A mutable 412 * reduction is one in which the reduced value is a mutable result container, 413 * such as an {@code ArrayList}, and elements are incorporated by updating 414 * the state of the result rather than by replacing the result. This 415 * produces a result equivalent to: 416 * <pre>{@code 417 * R result = supplier.get(); 418 * for (int element : this stream) 419 * accumulator.accept(result, element); 420 * return result; 421 * }</pre> 422 * 423 * <p>Like {@link #reduce(int, IntBinaryOperator)}, {@code collect} operations 424 * can be parallelized without requiring additional synchronization. 425 * 426 * <p>This is a <a href="package-summary.html#StreamOps">terminal 427 * operation</a>. 428 * 429 * @param <R> type of the result 430 * @param supplier a function that creates a new result container. For a 431 * parallel execution, this function may be called 432 * multiple times and must return a fresh value each time. 433 * @param accumulator an <a href="package-summary.html#Associativity">associative</a>, 434 * <a href="package-summary.html#NonInterference">non-interfering</a>, 435 * <a href="package-summary.html#Statelessness">stateless</a> 436 * function for incorporating an additional element into a result 437 * @param combiner 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 combining two values, which must be 441 * compatible with the accumulator function 442 * @return the result of the reduction 443 * @see Stream#collect(Supplier, BiConsumer, BiConsumer) 444 */ collect(Supplier<R> supplier, ObjIntConsumer<R> accumulator, BiConsumer<R, R> combiner)445 <R> R collect(Supplier<R> supplier, 446 ObjIntConsumer<R> accumulator, 447 BiConsumer<R, R> combiner); 448 449 /** 450 * Returns the sum of elements in this stream. This is a special case 451 * of a <a href="package-summary.html#Reduction">reduction</a> 452 * and is equivalent to: 453 * <pre>{@code 454 * return reduce(0, Integer::sum); 455 * }</pre> 456 * 457 * <p>This is a <a href="package-summary.html#StreamOps">terminal 458 * operation</a>. 459 * 460 * @return the sum of elements in this stream 461 */ sum()462 int sum(); 463 464 /** 465 * Returns an {@code OptionalInt} describing the minimum element of this 466 * stream, or an empty optional if this stream is empty. This is a special 467 * case of a <a href="package-summary.html#Reduction">reduction</a> 468 * and is equivalent to: 469 * <pre>{@code 470 * return reduce(Integer::min); 471 * }</pre> 472 * 473 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. 474 * 475 * @return an {@code OptionalInt} containing the minimum element of this 476 * stream, or an empty {@code OptionalInt} if the stream is empty 477 */ min()478 OptionalInt min(); 479 480 /** 481 * Returns an {@code OptionalInt} describing the maximum element of this 482 * stream, or an empty optional if this stream is empty. This is a special 483 * case of a <a href="package-summary.html#Reduction">reduction</a> 484 * and is equivalent to: 485 * <pre>{@code 486 * return reduce(Integer::max); 487 * }</pre> 488 * 489 * <p>This is a <a href="package-summary.html#StreamOps">terminal 490 * operation</a>. 491 * 492 * @return an {@code OptionalInt} containing the maximum element of this 493 * stream, or an empty {@code OptionalInt} if the stream is empty 494 */ max()495 OptionalInt max(); 496 497 /** 498 * Returns the count of elements in this stream. This is a special case of 499 * a <a href="package-summary.html#Reduction">reduction</a> and is 500 * equivalent to: 501 * <pre>{@code 502 * return mapToLong(e -> 1L).sum(); 503 * }</pre> 504 * 505 * <p>This is a <a href="package-summary.html#StreamOps">terminal operation</a>. 506 * 507 * @return the count of elements in this stream 508 */ count()509 long count(); 510 511 /** 512 * Returns an {@code OptionalDouble} describing the arithmetic mean of elements of 513 * this stream, or an empty optional if this stream is empty. This is a 514 * special case of a 515 * <a href="package-summary.html#Reduction">reduction</a>. 516 * 517 * <p>This is a <a href="package-summary.html#StreamOps">terminal 518 * operation</a>. 519 * 520 * @return an {@code OptionalDouble} containing the average element of this 521 * stream, or an empty optional if the stream is empty 522 */ average()523 OptionalDouble average(); 524 525 /** 526 * Returns an {@code IntSummaryStatistics} describing various 527 * summary data about the elements of this stream. This is a special 528 * case of a <a href="package-summary.html#Reduction">reduction</a>. 529 * 530 * <p>This is a <a href="package-summary.html#StreamOps">terminal 531 * operation</a>. 532 * 533 * @return an {@code IntSummaryStatistics} describing various summary data 534 * about the elements of this stream 535 */ summaryStatistics()536 IntSummaryStatistics summaryStatistics(); 537 538 /** 539 * Returns whether any elements of this stream match the provided 540 * predicate. May not evaluate the predicate on all elements if not 541 * necessary for determining the result. If the stream is empty then 542 * {@code false} is returned and the predicate is not evaluated. 543 * 544 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 545 * terminal operation</a>. 546 * 547 * @apiNote 548 * This method evaluates the <em>existential quantification</em> of the 549 * predicate over the elements of the stream (for some x P(x)). 550 * 551 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 552 * <a href="package-summary.html#Statelessness">stateless</a> 553 * predicate to apply to elements of this stream 554 * @return {@code true} if any elements of the stream match the provided 555 * predicate, otherwise {@code false} 556 */ anyMatch(IntPredicate predicate)557 boolean anyMatch(IntPredicate predicate); 558 559 /** 560 * Returns whether all elements of this stream match the provided predicate. 561 * May not evaluate the predicate on all elements if not necessary for 562 * determining the result. If the stream is empty then {@code true} is 563 * returned and the predicate is not evaluated. 564 * 565 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 566 * terminal operation</a>. 567 * 568 * @apiNote 569 * This method evaluates the <em>universal quantification</em> of the 570 * predicate over the elements of the stream (for all x P(x)). If the 571 * stream is empty, the quantification is said to be <em>vacuously 572 * satisfied</em> and is always {@code true} (regardless of P(x)). 573 * 574 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 575 * <a href="package-summary.html#Statelessness">stateless</a> 576 * predicate to apply to elements of this stream 577 * @return {@code true} if either all elements of the stream match the 578 * provided predicate or the stream is empty, otherwise {@code false} 579 */ allMatch(IntPredicate predicate)580 boolean allMatch(IntPredicate predicate); 581 582 /** 583 * Returns whether no elements of this stream match the provided predicate. 584 * May not evaluate the predicate on all elements if not necessary for 585 * determining the result. If the stream is empty then {@code true} is 586 * returned and the predicate is not evaluated. 587 * 588 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 589 * terminal operation</a>. 590 * 591 * @apiNote 592 * This method evaluates the <em>universal quantification</em> of the 593 * negated predicate over the elements of the stream (for all x ~P(x)). If 594 * the stream is empty, the quantification is said to be vacuously satisfied 595 * and is always {@code true}, regardless of P(x). 596 * 597 * @param predicate a <a href="package-summary.html#NonInterference">non-interfering</a>, 598 * <a href="package-summary.html#Statelessness">stateless</a> 599 * predicate to apply to elements of this stream 600 * @return {@code true} if either no elements of the stream match the 601 * provided predicate or the stream is empty, otherwise {@code false} 602 */ noneMatch(IntPredicate predicate)603 boolean noneMatch(IntPredicate predicate); 604 605 /** 606 * Returns an {@link OptionalInt} describing the first element of this 607 * stream, or an empty {@code OptionalInt} if the stream is empty. If the 608 * stream has no encounter order, then any element may be returned. 609 * 610 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 611 * terminal operation</a>. 612 * 613 * @return an {@code OptionalInt} describing the first element of this stream, 614 * or an empty {@code OptionalInt} if the stream is empty 615 */ findFirst()616 OptionalInt findFirst(); 617 618 /** 619 * Returns an {@link OptionalInt} describing some element of the stream, or 620 * an empty {@code OptionalInt} if the stream is empty. 621 * 622 * <p>This is a <a href="package-summary.html#StreamOps">short-circuiting 623 * terminal operation</a>. 624 * 625 * <p>The behavior of this operation is explicitly nondeterministic; it is 626 * free to select any element in the stream. This is to allow for maximal 627 * performance in parallel operations; the cost is that multiple invocations 628 * on the same source may not return the same result. (If a stable result 629 * is desired, use {@link #findFirst()} instead.) 630 * 631 * @return an {@code OptionalInt} describing some element of this stream, or 632 * an empty {@code OptionalInt} if the stream is empty 633 * @see #findFirst() 634 */ findAny()635 OptionalInt findAny(); 636 637 /** 638 * Returns a {@code LongStream} consisting of the elements of this stream, 639 * converted to {@code long}. 640 * 641 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 642 * operation</a>. 643 * 644 * @return a {@code LongStream} consisting of the elements of this stream, 645 * converted to {@code long} 646 */ asLongStream()647 LongStream asLongStream(); 648 649 /** 650 * Returns a {@code DoubleStream} consisting of the elements of this stream, 651 * converted to {@code double}. 652 * 653 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 654 * operation</a>. 655 * 656 * @return a {@code DoubleStream} consisting of the elements of this stream, 657 * converted to {@code double} 658 */ asDoubleStream()659 DoubleStream asDoubleStream(); 660 661 /** 662 * Returns a {@code Stream} consisting of the elements of this stream, 663 * each boxed to an {@code Integer}. 664 * 665 * <p>This is an <a href="package-summary.html#StreamOps">intermediate 666 * operation</a>. 667 * 668 * @return a {@code Stream} consistent of the elements of this stream, 669 * each boxed to an {@code Integer} 670 */ boxed()671 Stream<Integer> boxed(); 672 673 @Override sequential()674 IntStream sequential(); 675 676 @Override parallel()677 IntStream parallel(); 678 679 @Override iterator()680 PrimitiveIterator.OfInt iterator(); 681 682 @Override spliterator()683 Spliterator.OfInt spliterator(); 684 685 // Static factories 686 687 /** 688 * Returns a builder for an {@code IntStream}. 689 * 690 * @return a stream builder 691 */ builder()692 public static Builder builder() { 693 return new Streams.IntStreamBuilderImpl(); 694 } 695 696 /** 697 * Returns an empty sequential {@code IntStream}. 698 * 699 * @return an empty sequential stream 700 */ empty()701 public static IntStream empty() { 702 return StreamSupport.intStream(Spliterators.emptyIntSpliterator(), false); 703 } 704 705 /** 706 * Returns a sequential {@code IntStream} containing a single element. 707 * 708 * @param t the single element 709 * @return a singleton sequential stream 710 */ of(int t)711 public static IntStream of(int t) { 712 return StreamSupport.intStream(new Streams.IntStreamBuilderImpl(t), false); 713 } 714 715 /** 716 * Returns a sequential ordered stream whose elements are the specified values. 717 * 718 * @param values the elements of the new stream 719 * @return the new stream 720 */ of(int... values)721 public static IntStream of(int... values) { 722 return Arrays.stream(values); 723 } 724 725 /** 726 * Returns an infinite sequential ordered {@code IntStream} produced by iterative 727 * application of a function {@code f} to an initial element {@code seed}, 728 * producing a {@code Stream} consisting of {@code seed}, {@code f(seed)}, 729 * {@code f(f(seed))}, etc. 730 * 731 * <p>The first element (position {@code 0}) in the {@code IntStream} will be 732 * the provided {@code seed}. For {@code n > 0}, the element at position 733 * {@code n}, will be the result of applying the function {@code f} to the 734 * element at position {@code n - 1}. 735 * 736 * @param seed the initial element 737 * @param f a function to be applied to to the previous element to produce 738 * a new element 739 * @return A new sequential {@code IntStream} 740 */ iterate(final int seed, final IntUnaryOperator f)741 public static IntStream iterate(final int seed, final IntUnaryOperator f) { 742 Objects.requireNonNull(f); 743 final PrimitiveIterator.OfInt iterator = new PrimitiveIterator.OfInt() { 744 int t = seed; 745 746 @Override 747 public boolean hasNext() { 748 return true; 749 } 750 751 @Override 752 public int nextInt() { 753 int v = t; 754 t = f.applyAsInt(t); 755 return v; 756 } 757 }; 758 return StreamSupport.intStream(Spliterators.spliteratorUnknownSize( 759 iterator, 760 Spliterator.ORDERED | Spliterator.IMMUTABLE | Spliterator.NONNULL), false); 761 } 762 763 /** 764 * Returns an infinite sequential unordered stream where each element is 765 * generated by the provided {@code IntSupplier}. This is suitable for 766 * generating constant streams, streams of random elements, etc. 767 * 768 * @param s the {@code IntSupplier} for generated elements 769 * @return a new infinite sequential unordered {@code IntStream} 770 */ generate(IntSupplier s)771 public static IntStream generate(IntSupplier s) { 772 Objects.requireNonNull(s); 773 return StreamSupport.intStream( 774 new StreamSpliterators.InfiniteSupplyingSpliterator.OfInt(Long.MAX_VALUE, s), false); 775 } 776 777 /** 778 * Returns a sequential ordered {@code IntStream} from {@code startInclusive} 779 * (inclusive) to {@code endExclusive} (exclusive) by an incremental step of 780 * {@code 1}. 781 * 782 * @apiNote 783 * <p>An equivalent sequence of increasing values can be produced 784 * sequentially using a {@code for} loop as follows: 785 * <pre>{@code 786 * for (int i = startInclusive; i < endExclusive ; i++) { ... } 787 * }</pre> 788 * 789 * @param startInclusive the (inclusive) initial value 790 * @param endExclusive the exclusive upper bound 791 * @return a sequential {@code IntStream} for the range of {@code int} 792 * elements 793 */ range(int startInclusive, int endExclusive)794 public static IntStream range(int startInclusive, int endExclusive) { 795 if (startInclusive >= endExclusive) { 796 return empty(); 797 } else { 798 return StreamSupport.intStream( 799 new Streams.RangeIntSpliterator(startInclusive, endExclusive, false), false); 800 } 801 } 802 803 /** 804 * Returns a sequential ordered {@code IntStream} 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 (int 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 IntStream} for the range of {@code int} 818 * elements 819 */ rangeClosed(int startInclusive, int endInclusive)820 public static IntStream rangeClosed(int startInclusive, int endInclusive) { 821 if (startInclusive > endInclusive) { 822 return empty(); 823 } else { 824 return StreamSupport.intStream( 825 new Streams.RangeIntSpliterator(startInclusive, endInclusive, true), false); 826 } 827 } 828 829 /** 830 * Creates a lazily concatenated stream whose elements are all the 831 * elements of the first stream followed by all the elements of the 832 * second stream. The resulting stream is ordered if both 833 * of the input streams are ordered, and parallel if either of the input 834 * streams is parallel. When the resulting stream is closed, the close 835 * handlers for both input streams are invoked. 836 * 837 * @implNote 838 * Use caution when constructing streams from repeated concatenation. 839 * Accessing an element of a deeply concatenated stream can result in deep 840 * call chains, or even {@code StackOverflowException}. 841 * 842 * @param a the first stream 843 * @param b the second stream 844 * @return the concatenation of the two input streams 845 */ concat(IntStream a, IntStream b)846 public static IntStream concat(IntStream a, IntStream b) { 847 Objects.requireNonNull(a); 848 Objects.requireNonNull(b); 849 850 Spliterator.OfInt split = new Streams.ConcatSpliterator.OfInt( 851 a.spliterator(), b.spliterator()); 852 IntStream stream = StreamSupport.intStream(split, a.isParallel() || b.isParallel()); 853 return stream.onClose(Streams.composedClose(a, b)); 854 } 855 856 /** 857 * A mutable builder for an {@code IntStream}. 858 * 859 * <p>A stream builder has a lifecycle, which starts in a building 860 * phase, during which elements can be added, and then transitions to a built 861 * phase, after which elements may not be added. The built phase 862 * begins when the {@link #build()} method is called, which creates an 863 * ordered stream whose elements are the elements that were added to the 864 * stream builder, in the order they were added. 865 * 866 * @see IntStream#builder() 867 * @since 1.8 868 */ 869 public interface Builder extends IntConsumer { 870 871 /** 872 * Adds an element to the stream being built. 873 * 874 * @throws IllegalStateException if the builder has already transitioned 875 * to the built state 876 */ 877 @Override accept(int t)878 void accept(int t); 879 880 /** 881 * Adds an element to the stream being built. 882 * 883 * @implSpec 884 * The default implementation behaves as if: 885 * <pre>{@code 886 * accept(t) 887 * return this; 888 * }</pre> 889 * 890 * @param t the element to add 891 * @return {@code this} builder 892 * @throws IllegalStateException if the builder has already transitioned 893 * to the built state 894 */ add(int t)895 default Builder add(int t) { 896 accept(t); 897 return this; 898 } 899 900 /** 901 * Builds the stream, transitioning this builder to the built state. 902 * An {@code IllegalStateException} is thrown if there are further 903 * attempts to operate on the builder after it has entered the built 904 * state. 905 * 906 * @return the built stream 907 * @throws IllegalStateException if the builder has already transitioned to 908 * the built state 909 */ build()910 IntStream build(); 911 } 912 } 913