1 /*
   2  * Copyright (c) 1997, 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 
  26 package javany.util;
  27 
  28 import javany.util.function.Predicate;
  29 
  30 import java.util.Objects;
  31 
  32 /**
  33  * The root interface in the <i>collection hierarchy</i>.  A collection
  34  * represents a group of objects, known as its <i>elements</i>.  Some
  35  * collections allow duplicate elements and others do not.  Some are ordered
  36  * and others unordered.  The JDK does not provide any <i>direct</i>
  37  * implementations of this interface: it provides implementations of more
  38  * specific subinterfaces like <tt>Set</tt> and <tt>List</tt>.  This interface
  39  * is typically used to pass collections around and manipulate them where
  40  * maximum generality is desired.
  41  *
  42  * <p><i>Bags</i> or <i>multisets</i> (unordered collections that may contain
  43  * duplicate elements) should implement this interface directly.
  44  *
  45  * <p>All general-purpose <tt>Collection</tt> implementation classes (which
  46  * typically implement <tt>Collection</tt> indirectly through one of its
  47  * subinterfaces) should provide two "standard" constructors: a void (no
  48  * arguments) constructor, which creates an empty collection, and a
  49  * constructor with a single argument of type <tt>Collection</tt>, which
  50  * creates a new collection with the same elements as its argument.  In
  51  * effect, the latter constructor allows the user to copy any collection,
  52  * producing an equivalent collection of the desired implementation type.
  53  * There is no way to enforce this convention (as interfaces cannot contain
  54  * constructors) but all of the general-purpose <tt>Collection</tt>
  55  * implementations in the Java platform libraries comply.
  56  *
  57  * <p>The "destructive" methods contained in this interface, that is, the
  58  * methods that modify the collection on which they operate, are specified to
  59  * throw <tt>UnsupportedOperationException</tt> if this collection does not
  60  * support the operation.  If this is the case, these methods may, but are not
  61  * required to, throw an <tt>UnsupportedOperationException</tt> if the
  62  * invocation would have no effect on the collection.  For example, invoking
  63  * the {@link #addAll(Collection)} method on an unmodifiable collection may,
  64  * but is not required to, throw the exception if the collection to be added
  65  * is empty.
  66  *
  67  * <p><a name="optional-restrictions">
  68  * Some collection implementations have restrictions on the elements that
  69  * they may contain.</a>  For example, some implementations prohibit null elements,
  70  * and some have restrictions on the types of their elements.  Attempting to
  71  * add an ineligible element throws an unchecked exception, typically
  72  * <tt>NullPointerException</tt> or <tt>ClassCastException</tt>.  Attempting
  73  * to query the presence of an ineligible element may throw an exception,
  74  * or it may simply return false; some implementations will exhibit the former
  75  * behavior and some will exhibit the latter.  More generally, attempting an
  76  * operation on an ineligible element whose completion would not result in
  77  * the insertion of an ineligible element into the collection may throw an
  78  * exception or it may succeed, at the option of the implementation.
  79  * Such exceptions are marked as "optional" in the specification for this
  80  * interface.
  81  *
  82  * <p>It is up to each collection to determine its own synchronization
  83  * policy.  In the absence of a stronger guarantee by the
  84  * implementation, undefined behavior may result from the invocation
  85  * of any method on a collection that is being mutated by another
  86  * thread; this includes direct invocations, passing the collection to
  87  * a method that might perform invocations, and using an existing
  88  * iterator to examine the collection.
  89  *
  90  * <p>Many methods in Collections Framework interfaces are defined in
  91  * terms of the {@link Object#equals(Object) equals} method.  For example,
  92  * the specification for the {@link #contains(Object) contains(Object o)}
  93  * method says: "returns <tt>true</tt> if and only if this collection
  94  * contains at least one element <tt>e</tt> such that
  95  * <tt>(o==null ? e==null : o.equals(e))</tt>."  This specification should
  96  * <i>not</i> be construed to imply that invoking <tt>Collection.contains</tt>
  97  * with a non-null argument <tt>o</tt> will cause <tt>o.equals(e)</tt> to be
  98  * invoked for any element <tt>e</tt>.  Implementations are free to implement
  99  * optimizations whereby the <tt>equals</tt> invocation is avoided, for
 100  * example, by first comparing the hash codes of the two elements.  (The
 101  * {@link Object#hashCode()} specification guarantees that two objects with
 102  * unequal hash codes cannot be equal.)  More generally, implementations of
 103  * the various Collections Framework interfaces are free to take advantage of
 104  * the specified behavior of underlying {@link Object} methods wherever the
 105  * implementor deems it appropriate.
 106  *
 107  * <p>Some collection operations which perform recursive traversal of the
 108  * collection may fail with an exception for self-referential instances where
 109  * the collection directly or indirectly contains itself. This includes the
 110  * {@code clone()}, {@code equals()}, {@code hashCode()} and {@code toString()}
 111  * methods. Implementations may optionally handle the self-referential scenario,
 112  * however most current implementations do not do so.
 113  *
 114  * <p>This interface is a member of the
 115  * <a href="{@docRoot}/../technotes/guides/collections/index.html">
 116  * Java Collections Framework</a>.
 117  *
 118  * @implSpec
 119  * The default method implementations (inherited or otherwise) do not apply any
 120  * synchronization protocol.  If a {@code Collection} implementation has a
 121  * specific synchronization protocol, then it must override default
 122  * implementations to apply that protocol.
 123  *
 124  * @param <E> the type of elements in this collection
 125  *
 126  * @author  Josh Bloch
 127  * @author  Neal Gafter
 128  * @see     Set
 129  * @see     List
 130  * @see     Map
 131  * @see     SortedSet
 132  * @see     SortedMap
 133  * @see     HashSet
 134  * @see     TreeSet
 135  * @see     ArrayList
 136  * @see     LinkedList
 137  * @see     Vector
 138  * @see     Collections
 139  * @see     Arrays
 140  * @see     AbstractCollection
 141  * @since 1.2
 142  */
 143 
 144 public interface Collection<any E> extends javany.lang.Iterable<E> {
 145     // Query Operations
 146 
 147     /**
 148      * Returns the number of elements in this collection.  If this collection
 149      * contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
 150      * <tt>Integer.MAX_VALUE</tt>.
 151      *
 152      * @return the number of elements in this collection
 153      */
 154     int size();
 155 
 156     /**
 157      * Returns <tt>true</tt> if this collection contains no elements.
 158      *
 159      * @return <tt>true</tt> if this collection contains no elements
 160      */
 161     boolean isEmpty();
 162 
 163     /**
 164      * Returns <tt>true</tt> if this collection contains the specified element.
 165      * More formally, returns <tt>true</tt> if and only if this collection
 166      * contains at least one element <tt>e</tt> such that
 167      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
 168      *
 169      * @param o element whose presence in this collection is to be tested
 170      * @return <tt>true</tt> if this collection contains the specified
 171      *         element
 172      * @throws ClassCastException if the type of the specified element
 173      *         is incompatible with this collection
 174      *         (<a href="#optional-restrictions">optional</a>)
 175      * @throws NullPointerException if the specified element is null and this
 176      *         collection does not permit null elements
 177      *         (<a href="#optional-restrictions">optional</a>)
 178      */
 179     boolean contains(Object o);
 180 
 181     default boolean containsElement(E e) {
 182         Iterator<E> it = iterator();
 183         while (it.hasNext())
 184             if (Any.equals(e, it.next()))
 185                 return true;
 186         return false;
 187     }
 188 
 189     /**
 190      * Returns an iterator over the elements in this collection.  There are no
 191      * guarantees concerning the order in which the elements are returned
 192      * (unless this collection is an instance of some class that provides a
 193      * guarantee).
 194      *
 195      * @return an <tt>Iterator</tt> over the elements in this collection
 196      */
 197     Iterator<E> iterator();
 198 
 199     /**
 200      * Returns an array containing all of the elements in this collection.
 201      * If this collection makes any guarantees as to what order its elements
 202      * are returned by its iterator, this method must return the elements in
 203      * the same order.
 204      *
 205      * <p>The returned array will be "safe" in that no references to it are
 206      * maintained by this collection.  (In other words, this method must
 207      * allocate a new array even if this collection is backed by an array).
 208      * The caller is thus free to modify the returned array.
 209      *
 210      * <p>This method acts as bridge between array-based and collection-based
 211      * APIs.
 212      *
 213      * @return an array containing all of the elements in this collection
 214      */
 215     Object[] toArray();
 216 
 217     /**
 218      * Returns an array containing all of the elements in this collection;
 219      * the runtime type of the returned array is that of the specified array.
 220      * If the collection fits in the specified array, it is returned therein.
 221      * Otherwise, a new array is allocated with the runtime type of the
 222      * specified array and the size of this collection.
 223      *
 224      * <p>If this collection fits in the specified array with room to spare
 225      * (i.e., the array has more elements than this collection), the element
 226      * in the array immediately following the end of the collection is set to
 227      * <tt>null</tt>.  (This is useful in determining the length of this
 228      * collection <i>only</i> if the caller knows that this collection does
 229      * not contain any <tt>null</tt> elements.)
 230      *
 231      * <p>If this collection makes any guarantees as to what order its elements
 232      * are returned by its iterator, this method must return the elements in
 233      * the same order.
 234      *
 235      * <p>Like the {@link #toArray()} method, this method acts as bridge between
 236      * array-based and collection-based APIs.  Further, this method allows
 237      * precise control over the runtime type of the output array, and may,
 238      * under certain circumstances, be used to save allocation costs.
 239      *
 240      * <p>Suppose <tt>x</tt> is a collection known to contain only strings.
 241      * The following code can be used to dump the collection into a newly
 242      * allocated array of <tt>String</tt>:
 243      *
 244      * <pre>
 245      *     String[] y = x.toArray(new String[0]);</pre>
 246      *
 247      * Note that <tt>toArray(new Object[0])</tt> is identical in function to
 248      * <tt>toArray()</tt>.
 249      *
 250      * @param <T> the runtime type of the array to contain the collection
 251      * @param a the array into which the elements of this collection are to be
 252      *        stored, if it is big enough; otherwise, a new array of the same
 253      *        runtime type is allocated for this purpose.
 254      * @return an array containing all of the elements in this collection
 255      * @throws ArrayStoreException if the runtime type of the specified array
 256      *         is not a supertype of the runtime type of every element in
 257      *         this collection
 258      * @throws NullPointerException if the specified array is null
 259      */
 260     <any T> T[] toArray(T[] a);
 261 
 262     // Modification Operations
 263 
 264     /**
 265      * Ensures that this collection contains the specified element (optional
 266      * operation).  Returns <tt>true</tt> if this collection changed as a
 267      * result of the call.  (Returns <tt>false</tt> if this collection does
 268      * not permit duplicates and already contains the specified element.)<p>
 269      *
 270      * Collections that support this operation may place limitations on what
 271      * elements may be added to this collection.  In particular, some
 272      * collections will refuse to add <tt>null</tt> elements, and others will
 273      * impose restrictions on the type of elements that may be added.
 274      * Collection classes should clearly specify in their documentation any
 275      * restrictions on what elements may be added.<p>
 276      *
 277      * If a collection refuses to add a particular element for any reason
 278      * other than that it already contains the element, it <i>must</i> throw
 279      * an exception (rather than returning <tt>false</tt>).  This preserves
 280      * the invariant that a collection always contains the specified element
 281      * after this call returns.
 282      *
 283      * @param e element whose presence in this collection is to be ensured
 284      * @return <tt>true</tt> if this collection changed as a result of the
 285      *         call
 286      * @throws UnsupportedOperationException if the <tt>add</tt> operation
 287      *         is not supported by this collection
 288      * @throws ClassCastException if the class of the specified element
 289      *         prevents it from being added to this collection
 290      * @throws NullPointerException if the specified element is null and this
 291      *         collection does not permit null elements
 292      * @throws IllegalArgumentException if some property of the element
 293      *         prevents it from being added to this collection
 294      * @throws IllegalStateException if the element cannot be added at this
 295      *         time due to insertion restrictions
 296      */
 297     boolean add(E e);
 298 
 299     /**
 300      * Removes a single instance of the specified element from this
 301      * collection, if it is present (optional operation).  More formally,
 302      * removes an element <tt>e</tt> such that
 303      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>, if
 304      * this collection contains one or more such elements.  Returns
 305      * <tt>true</tt> if this collection contained the specified element (or
 306      * equivalently, if this collection changed as a result of the call).
 307      *
 308      * @param o element to be removed from this collection, if present
 309      * @return <tt>true</tt> if an element was removed as a result of this call
 310      * @throws ClassCastException if the type of the specified element
 311      *         is incompatible with this collection
 312      *         (<a href="#optional-restrictions">optional</a>)
 313      * @throws NullPointerException if the specified element is null and this
 314      *         collection does not permit null elements
 315      *         (<a href="#optional-restrictions">optional</a>)
 316      * @throws UnsupportedOperationException if the <tt>remove</tt> operation
 317      *         is not supported by this collection
 318      */
 319     boolean remove(Object o);
 320 
 321     default boolean removeElement(E e) {
 322         Iterator<E> it = iterator();
 323         while (it.hasNext()) {
 324             if (Any.equals(e, it.next())) {
 325                 it.remove();
 326                 return true;
 327             }
 328         }
 329         return false;
 330     }
 331 
 332     // Bulk Operations
 333 
 334     /**
 335      * Returns <tt>true</tt> if this collection contains all of the elements
 336      * in the specified collection.
 337      *
 338      * @param  c collection to be checked for containment in this collection
 339      * @return <tt>true</tt> if this collection contains all of the elements
 340      *         in the specified collection
 341      * @throws ClassCastException if the types of one or more elements
 342      *         in the specified collection are incompatible with this
 343      *         collection
 344      *         (<a href="#optional-restrictions">optional</a>)
 345      * @throws NullPointerException if the specified collection contains one
 346      *         or more null elements and this collection does not permit null
 347      *         elements
 348      *         (<a href="#optional-restrictions">optional</a>),
 349      *         or if the specified collection is null.
 350      * @see    #contains(Object)
 351      */
 352     boolean containsAll(Collection<?> c);
 353 
 354     default boolean containsAllElements(Collection<? extends E> c) {
 355         Iterator<? extends E> it = c.iterator();
 356         while (it.hasNext()) {
 357             if (!containsElement(it.next())) {
 358                 return false;
 359             }
 360         }
 361         return true;
 362     }
 363 
 364     /**
 365      * Adds all of the elements in the specified collection to this collection
 366      * (optional operation).  The behavior of this operation is undefined if
 367      * the specified collection is modified while the operation is in progress.
 368      * (This implies that the behavior of this call is undefined if the
 369      * specified collection is this collection, and this collection is
 370      * nonempty.)
 371      *
 372      * @param c collection containing elements to be added to this collection
 373      * @return <tt>true</tt> if this collection changed as a result of the call
 374      * @throws UnsupportedOperationException if the <tt>addAll</tt> operation
 375      *         is not supported by this collection
 376      * @throws ClassCastException if the class of an element of the specified
 377      *         collection prevents it from being added to this collection
 378      * @throws NullPointerException if the specified collection contains a
 379      *         null element and this collection does not permit null elements,
 380      *         or if the specified collection is null
 381      * @throws IllegalArgumentException if some property of an element of the
 382      *         specified collection prevents it from being added to this
 383      *         collection
 384      * @throws IllegalStateException if not all the elements can be added at
 385      *         this time due to insertion restrictions
 386      * @see #add(Object)
 387      */
 388     boolean addAll(Collection<? extends E> c);
 389 
 390     /**
 391      * Removes all of this collection's elements that are also contained in the
 392      * specified collection (optional operation).  After this call returns,
 393      * this collection will contain no elements in common with the specified
 394      * collection.
 395      *
 396      * @param c collection containing elements to be removed from this collection
 397      * @return <tt>true</tt> if this collection changed as a result of the
 398      *         call
 399      * @throws UnsupportedOperationException if the <tt>removeAll</tt> method
 400      *         is not supported by this collection
 401      * @throws ClassCastException if the types of one or more elements
 402      *         in this collection are incompatible with the specified
 403      *         collection
 404      *         (<a href="#optional-restrictions">optional</a>)
 405      * @throws NullPointerException if this collection contains one or more
 406      *         null elements and the specified collection does not support
 407      *         null elements
 408      *         (<a href="#optional-restrictions">optional</a>),
 409      *         or if the specified collection is null
 410      * @see #remove(Object)
 411      * @see #contains(Object)
 412      */
 413     boolean removeAll(Collection<?> c);
 414 
 415     default boolean removeAllElements(Collection<E> c) {
 416         Objects.requireNonNull(c);
 417         boolean modified = false;
 418         Iterator<E> it = iterator();
 419         while (it.hasNext()) {
 420             if (c.containsElement(it.next())) {
 421                 it.remove();
 422                 modified = true;
 423             }
 424         }
 425         return modified;
 426     }
 427 
 428     /**
 429      * Removes all of the elements of this collection that satisfy the given
 430      * predicate.  Errors or runtime exceptions thrown during iteration or by
 431      * the predicate are relayed to the caller.
 432      *
 433      * @implSpec
 434      * The default implementation traverses all elements of the collection using
 435      * its {@link #iterator}.  Each matching element is removed using
 436      * {@link Iterator#remove()}.  If the collection's iterator does not
 437      * support removal then an {@code UnsupportedOperationException} will be
 438      * thrown on the first matching element.
 439      *
 440      * @param filter a predicate which returns {@code true} for elements to be
 441      *        removed
 442      * @return {@code true} if any elements were removed
 443      * @throws NullPointerException if the specified filter is null
 444      * @throws UnsupportedOperationException if elements cannot be removed
 445      *         from this collection.  Implementations may throw this exception if a
 446      *         matching element cannot be removed or if, in general, removal is not
 447      *         supported.
 448      * @since 1.8
 449      */
 450     default boolean removeIf(Predicate<? super E> filter) {
 451         Objects.requireNonNull(filter);
 452         boolean removed = false;
 453         final Iterator<E> each = iterator();
 454         while (each.hasNext()) {
 455             if (filter.test(each.next())) {
 456                 each.remove();
 457                 removed = true;
 458             }
 459         }
 460         return removed;
 461     }
 462 
 463     /**
 464      * Retains only the elements in this collection that are contained in the
 465      * specified collection (optional operation).  In other words, removes from
 466      * this collection all of its elements that are not contained in the
 467      * specified collection.
 468      *
 469      * @param c collection containing elements to be retained in this collection
 470      * @return <tt>true</tt> if this collection changed as a result of the call
 471      * @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
 472      *         is not supported by this collection
 473      * @throws ClassCastException if the types of one or more elements
 474      *         in this collection are incompatible with the specified
 475      *         collection
 476      *         (<a href="#optional-restrictions">optional</a>)
 477      * @throws NullPointerException if this collection contains one or more
 478      *         null elements and the specified collection does not permit null
 479      *         elements
 480      *         (<a href="#optional-restrictions">optional</a>),
 481      *         or if the specified collection is null
 482      * @see #remove(Object)
 483      * @see #contains(Object)
 484      */
 485     boolean retainAll(Collection<?> c);
 486 
 487     default boolean retainAllElements(Collection<E> c) {
 488         Objects.requireNonNull(c);
 489         boolean modified = false;
 490         Iterator<E> it = iterator();
 491         while (it.hasNext()) {
 492             if (!c.containsElement(it.next())) {
 493                 it.remove();
 494                 modified = true;
 495             }
 496         }
 497         return modified;
 498     }
 499 
 500     /**
 501      * Removes all of the elements from this collection (optional operation).
 502      * The collection will be empty after this method returns.
 503      *
 504      * @throws UnsupportedOperationException if the <tt>clear</tt> operation
 505      *         is not supported by this collection
 506      */
 507     void clear();
 508 
 509 
 510     // Comparison and hashing
 511 
 512     /**
 513      * Compares the specified object with this collection for equality. <p>
 514      *
 515      * While the <tt>Collection</tt> interface adds no stipulations to the
 516      * general contract for the <tt>Object.equals</tt>, programmers who
 517      * implement the <tt>Collection</tt> interface "directly" (in other words,
 518      * create a class that is a <tt>Collection</tt> but is not a <tt>Set</tt>
 519      * or a <tt>List</tt>) must exercise care if they choose to override the
 520      * <tt>Object.equals</tt>.  It is not necessary to do so, and the simplest
 521      * course of action is to rely on <tt>Object</tt>'s implementation, but
 522      * the implementor may wish to implement a "value comparison" in place of
 523      * the default "reference comparison."  (The <tt>List</tt> and
 524      * <tt>Set</tt> interfaces mandate such value comparisons.)<p>
 525      *
 526      * The general contract for the <tt>Object.equals</tt> method states that
 527      * equals must be symmetric (in other words, <tt>a.equals(b)</tt> if and
 528      * only if <tt>b.equals(a)</tt>).  The contracts for <tt>List.equals</tt>
 529      * and <tt>Set.equals</tt> state that lists are only equal to other lists,
 530      * and sets to other sets.  Thus, a custom <tt>equals</tt> method for a
 531      * collection class that implements neither the <tt>List</tt> nor
 532      * <tt>Set</tt> interface must return <tt>false</tt> when this collection
 533      * is compared to any list or set.  (By the same logic, it is not possible
 534      * to write a class that correctly implements both the <tt>Set</tt> and
 535      * <tt>List</tt> interfaces.)
 536      *
 537      * @param o object to be compared for equality with this collection
 538      * @return <tt>true</tt> if the specified object is equal to this
 539      * collection
 540      *
 541      * @see Object#equals(Object)
 542      * @see Set#equals(Object)
 543      * @see List#equals(Object)
 544      */
 545     boolean equals(Object o);
 546 
 547     /**
 548      * Returns the hash code value for this collection.  While the
 549      * <tt>Collection</tt> interface adds no stipulations to the general
 550      * contract for the <tt>Object.hashCode</tt> method, programmers should
 551      * take note that any class that overrides the <tt>Object.equals</tt>
 552      * method must also override the <tt>Object.hashCode</tt> method in order
 553      * to satisfy the general contract for the <tt>Object.hashCode</tt> method.
 554      * In particular, <tt>c1.equals(c2)</tt> implies that
 555      * <tt>c1.hashCode()==c2.hashCode()</tt>.
 556      *
 557      * @return the hash code value for this collection
 558      *
 559      * @see Object#hashCode()
 560      * @see Object#equals(Object)
 561      */
 562     int hashCode();
 563 
 564     /**
 565      * Creates a {@link Spliterator} over the elements in this collection.
 566      *
 567      * Implementations should document characteristic values reported by the
 568      * spliterator.  Such characteristic values are not required to be reported
 569      * if the spliterator reports {@link Spliterator#SIZED} and this collection
 570      * contains no elements.
 571      *
 572      * <p>The default implementation should be overridden by subclasses that
 573      * can return a more efficient spliterator.  In order to
 574      * preserve expected laziness behavior for the {@link #stream()} and
 575      * {@link #parallelStream()} methods, spliterators should either have the
 576      * characteristic of {@code IMMUTABLE} or {@code CONCURRENT}, or be
 577      * <em><a href="Spliterator.html#binding">late-binding</a></em>.
 578      * If none of these is practical, the overriding class should describe the
 579      * spliterator's documented policy of binding and structural interference,
 580      * and should override the {@link #stream()} and {@link #parallelStream()}
 581      * methods to create streams using a {@code Supplier} of the spliterator,
 582      * as in:
 583      * <pre>{@code
 584      *     Stream<E> s = StreamSupport.stream(() -> spliterator(), spliteratorCharacteristics)
 585      * }</pre>
 586      * <p>These requirements ensure that streams produced by the
 587      * {@link #stream()} and {@link #parallelStream()} methods will reflect the
 588      * contents of the collection as of initiation of the terminal stream
 589      * operation.
 590      *
 591      * @implSpec
 592      * The default implementation creates a
 593      * <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
 594      * from the collections's {@code Iterator}.  The spliterator inherits the
 595      * <em>fail-fast</em> properties of the collection's iterator.
 596      * <p>
 597      * The created {@code Spliterator} reports {@link Spliterator#SIZED}.
 598      *
 599      * @implNote
 600      * The created {@code Spliterator} additionally reports
 601      * {@link Spliterator#SUBSIZED}.
 602      *
 603      * <p>If a spliterator covers no elements then the reporting of additional
 604      * characteristic values, beyond that of {@code SIZED} and {@code SUBSIZED},
 605      * does not aid clients to control, specialize or simplify computation.
 606      * However, this does enable shared use of an immutable and empty
 607      * spliterator instance (see {@link Spliterators#emptySpliterator()}) for
 608      * empty collections, and enables clients to determine if such a spliterator
 609      * covers no elements.
 610      *
 611      * @return a {@code Spliterator} over the elements in this collection
 612      * @since 1.8
 613      */
 614 //    @Override
 615 //    default Spliterator<E> spliterator() {
 616 //        return Spliterators.spliterator(this, 0);
 617 //    }
 618 
 619     /**
 620      * Returns a sequential {@code Stream} with this collection as its source.
 621      *
 622      * <p>This method should be overridden when the {@link #spliterator()}
 623      * method cannot return a spliterator that is {@code IMMUTABLE},
 624      * {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}
 625      * for details.)
 626      *
 627      * @implSpec
 628      * The default implementation creates a sequential {@code Stream} from the
 629      * collection's {@code Spliterator}.
 630      *
 631      * @return a sequential {@code Stream} over the elements in this collection
 632      * @since 1.8
 633      */
 634 //    default Stream<E> stream() {
 635 //        return StreamSupport.stream(spliterator(), false);
 636 //    }
 637 
 638     /**
 639      * Returns a possibly parallel {@code Stream} with this collection as its
 640      * source.  It is allowable for this method to return a sequential stream.
 641      *
 642      * <p>This method should be overridden when the {@link #spliterator()}
 643      * method cannot return a spliterator that is {@code IMMUTABLE},
 644      * {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}
 645      * for details.)
 646      *
 647      * @implSpec
 648      * The default implementation creates a parallel {@code Stream} from the
 649      * collection's {@code Spliterator}.
 650      *
 651      * @return a possibly parallel {@code Stream} over the elements in this
 652      * collection
 653      * @since 1.8
 654      */
 655 //    default Stream<E> parallelStream() {
 656 //        return StreamSupport.stream(spliterator(), true);
 657 //    }
 658 }
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