/*
 
* Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 
*
 
* This code is free software; you can redistribute it and/or modify it
 
* under the terms of the GNU General Public License version 2 only, as
 
* published by the Free Software Foundation.
  
Oracle designates this
 
* particular file as subject to the "Classpath" exception as provided
 
* by Oracle in the LICENSE file that accompanied this code.
 
*
 
* This code is distributed in the hope that it will be useful, but WITHOUT
 
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 
* FITNESS FOR A PARTICULAR PURPOSE.
  
See the GNU General Public License
 
* version 2 for more details (a copy is included in the LICENSE file that
 
* accompanied this code).
 
*
 
* You should have received a copy of the GNU General Public License version
 
* 2 along with this work; if not, write to the Free Software Foundation,
 
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 
*
 
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 
* or visit www.oracle.com if you need additional information or have any
 
* questions.
 
*/

package java.util;

import java.util.function.Predicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

/**
 
* The root interface in the <i>collection hierarchy</i>.
  
A collection
 
* represents a group of objects, known as its <i>elements</i>.
  
Some
 
* collections allow duplicate elements and others do not.
  
Some are ordered
 
* and others unordered.
  
The JDK does not provide any <i>direct</i>
 
* implementations of this interface: it provides implementations of more
 
* specific subinterfaces like <tt>Set</tt> and <tt>List</tt>.
  
This interface
 
* is typically used to pass collections around and manipulate them where
 
* maximum generality is desired.
 
*
 
* <p><i>Bags</i> or <i>multisets</i> (unordered collections that may contain
 
* duplicate elements) should implement this interface directly.
 
*
 
* <p>All general-purpose <tt>Collection</tt> implementation classes (which
 
* typically implement <tt>Collection</tt> indirectly through one of its
 
* subinterfaces) should provide two "standard" constructors: a void (no
 
* arguments) constructor, which creates an empty collection, and a
 
* constructor with a single argument of type <tt>Collection</tt>, which
 
* creates a new collection with the same elements as its argument.
  
In
 
* effect, the latter constructor allows the user to copy any collection,
 
* producing an equivalent collection of the desired implementation type.
 
* There is no way to enforce this convention (as interfaces cannot contain
 
* constructors) but all of the general-purpose <tt>Collection</tt>
 
* implementations in the Java platform libraries comply.
 
*
 
* <p>The "destructive" methods contained in this interface, that is, the
 
* methods that modify the collection on which they operate, are specified to
 
* throw <tt>UnsupportedOperationException</tt> if this collection does not
 
* support the operation.
  
If this is the case, these methods may, but are not
 
* required to, throw an <tt>UnsupportedOperationException</tt> if the
 
* invocation would have no effect on the collection.
  
For example, invoking
 
* the {@link #addAll(Collection)} method on an unmodifiable collection may,
 
* but is not required to, throw the exception if the collection to be added
 
* is empty.
 
*
 
* <p><a name="optional-restrictions">
 
* Some collection implementations have restrictions on the elements that
 
* they may contain.</a>
  
For example, some implementations prohibit null elements,
 
* and some have restrictions on the types of their elements.
  
Attempting to
 
* add an ineligible element throws an unchecked exception, typically
 
* <tt>NullPointerException</tt> or <tt>ClassCastException</tt>.
  
Attempting
 
* to query the presence of an ineligible element may throw an exception,
 
* or it may simply return false; some implementations will exhibit the former
 
* behavior and some will exhibit the latter.
  
More generally, attempting an
 
* operation on an ineligible element whose completion would not result in
 
* the insertion of an ineligible element into the collection may throw an
 
* exception or it may succeed, at the option of the implementation.
 
* Such exceptions are marked as "optional" in the specification for this
 
* interface.
 
*
 
* <p>It is up to each collection to determine its own synchronization
 
* policy.
  
In the absence of a stronger guarantee by the
 
* implementation, undefined behavior may result from the invocation
 
* of any method on a collection that is being mutated by another
 
* thread; this includes direct invocations, passing the collection to
 
* a method that might perform invocations, and using an existing
 
* iterator to examine the collection.
 
*
 
* <p>Many methods in Collections Framework interfaces are defined in
 
* terms of the {@link Object#equals(Object) equals} method.
  
For example,
 
* the specification for the {@link #contains(Object) contains(Object o)}
 
* method says: "returns <tt>true</tt> if and only if this collection
 
* contains at least one element <tt>e</tt> such that
 
* <tt>(o==null ? e==null : o.equals(e))</tt>."
  
This specification should
 
* <i>not</i> be construed to imply that invoking <tt>Collection.contains</tt>
 
* with a non-null argument <tt>o</tt> will cause <tt>o.equals(e)</tt> to be
 
* invoked for any element <tt>e</tt>.
  
Implementations are free to implement
 
* optimizations whereby the <tt>equals</tt> invocation is avoided, for
 
* example, by first comparing the hash codes of the two elements.
  
(The
 
* {@link Object#hashCode()} specification guarantees that two objects with
 
* unequal hash codes cannot be equal.)
  
More generally, implementations of
 
* the various Collections Framework interfaces are free to take advantage of
 
* the specified behavior of underlying {@link Object} methods wherever the
 
* implementor deems it appropriate.
 
*
 
* <p>Some collection operations which perform recursive traversal of the
 
* collection may fail with an exception for self-referential instances where
 
* the collection directly or indirectly contains itself. This includes the
 
* {@code clone()}, {@code equals()}, {@code hashCode()} and {@code toString()}
 
* methods. Implementations may optionally handle the self-referential scenario,
 
* however most current implementations do not do so.
 
*
 
* <p>This interface is a member of the
 
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
 
* Java Collections Framework</a>.
 
*
 
* @implSpec
 
* The default method implementations (inherited or otherwise) do not apply any
 
* synchronization protocol.
  
If a {@code Collection} implementation has a
 
* specific synchronization protocol, then it must override default
 
* implementations to apply that protocol.
 
*
 
* @param <E> the type of elements in this collection
 
*
 
* @author
  
Josh Bloch
 
* @author
  
Neal Gafter
 
* @see
     
Set
 
* @see
     
List
 
* @see
     
Map
 
* @see
     
SortedSet
 
* @see
     
SortedMap
 
* @see
     
HashSet
 
* @see
     
TreeSet
 
* @see
     
ArrayList
 
* @see
     
LinkedList
 
* @see
     
Vector
 
* @see
     
Collections
 
* @see
     
Arrays
 
* @see
     
AbstractCollection
 
* @since 1.2
 
*/


public interface Collection<E> extends Iterable<E> {
    
// Query Operations

    
/**
     
* Returns the number of elements in this collection.
  
If this collection
     
* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
     
* <tt>Integer.MAX_VALUE</tt>.
     
*
     
* @return the number of elements in this collection
     
*/

    
int size();

    
/**
     
* Returns <tt>true</tt> if this collection contains no elements.
     
*
     
* @return <tt>true</tt> if this collection contains no elements
     
*/

    
boolean isEmpty();

    
/**
     
* Returns <tt>true</tt> if this collection contains the specified element.
     
* More formally, returns <tt>true</tt> if and only if this collection
     
* contains at least one element <tt>e</tt> such that
     
* <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
     
*
     
* @param o element whose presence in this collection is to be tested
     
* @return <tt>true</tt> if this collection contains the specified
     
*
         
element
     
* @throws ClassCastException if the type of the specified element
     
*
         
is incompatible with this collection
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
* @throws NullPointerException if the specified element is null and this
     
*
         
collection does not permit null elements
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
*/

    
boolean contains(Object o);

    
/**
     
* Returns an iterator over the elements in this collection.
  
There are no
     
* guarantees concerning the order in which the elements are returned
     
* (unless this collection is an instance of some class that provides a
     
* guarantee).
     
*
     
* @return an <tt>Iterator</tt> over the elements in this collection
     
*/

    
Iterator<E> iterator();

    
/**
     
* Returns an array containing all of the elements in this collection.
     
* If this collection makes any guarantees as to what order its elements
     
* are returned by its iterator, this method must return the elements in
     
* the same order.
     
*
     
* <p>The returned array will be "safe" in that no references to it are
     
* maintained by this collection.
  
(In other words, this method must
     
* allocate a new array even if this collection is backed by an array).
     
* The caller is thus free to modify the returned array.
     
*
     
* <p>This method acts as bridge between array-based and collection-based
     
* APIs.
     
*
     
* @return an array containing all of the elements in this collection
     
*/

    
Object[] toArray();

    
/**
     
* Returns an array containing all of the elements in this collection;
     
* the runtime type of the returned array is that of the specified array.
     
* If the collection fits in the specified array, it is returned therein.
     
* Otherwise, a new array is allocated with the runtime type of the
     
* specified array and the size of this collection.
     
*
     
* <p>If this collection fits in the specified array with room to spare
     
* (i.e., the array has more elements than this collection), the element
     
* in the array immediately following the end of the collection is set to
     
* <tt>null</tt>.
  
(This is useful in determining the length of this
     
* collection <i>only</i> if the caller knows that this collection does
     
* not contain any <tt>null</tt> elements.)
     
*
     
* <p>If this collection makes any guarantees as to what order its elements
     
* are returned by its iterator, this method must return the elements in
     
* the same order.
     
*
     
* <p>Like the
 
 
method, this method acts as bridge between
     
* array-based and collection-based APIs.
  
Further, this method allows
     
* precise control over the runtime type of the output array, and may,
     
* under certain circumstances, be used to save allocation costs.
     
*
     
* <p>Suppose <tt>x</tt> is a collection known to contain only strings.
     
* The following code can be used to dump the collection into a newly
     
* allocated array of <tt>String</tt>:
     
*
     
* <pre>
     
*String[] y = x.toArray(new String[0]);</pre>
     
*
     
* Note that <tt>toArray(new Object[0])</tt> is identical in function to
     
* <tt>toArray()</tt>.
     
*
     
* @param <T> the runtime type of the array to contain the collection
     
* @param a the array into which the elements of this collection are to be
     
*
        
stored, if it is big enough; otherwise, a new array of the same
     
*
        
runtime type is allocated for this purpose.
     
* @return an array containing all of the elements in this collection
     
* @throws ArrayStoreException if the runtime type of the specified array
     
*
         
is not a supertype of the runtime type of every element in
     
*
         
this collection
     
* @throws NullPointerException if the specified array is null
     
*/

    
<T> T[] toArray(T[] a);

    
// Modification Operations

    
/**
     
* Ensures that this collection contains the specified element (optional
     
* operation).
  
Returns <tt>true</tt> if this collection changed as a
     
* result of the call.
  
(Returns <tt>false</tt> if this collection does
     
* not permit duplicates and already contains the specified element.)<p>
     
*
     
* Collections that support this operation may place limitations on what
     
* elements may be added to this collection.
  
In particular, some
     
* collections will refuse to add <tt>null</tt> elements, and others will
     
* impose restrictions on the type of elements that may be added.
     
* Collection classes should clearly specify in their documentation any
     
* restrictions on what elements may be added.<p>
     
*
     
* If a collection refuses to add a particular element for any reason
     
* other than that it already contains the element, it <i>must</i> throw
     
* an exception (rather than returning <tt>false</tt>).
  
This preserves
     
* the invariant that a collection always contains the specified element
     
* after this call returns.
     
*
     
* @param e element whose presence in this collection is to be ensured
     
* @return <tt>true</tt> if this collection changed as a result of the
     
*
         
call
     
* @throws UnsupportedOperationException if the <tt>add</tt> operation
     
*
         
is not supported by this collection
     
* @throws ClassCastException if the class of the specified element
     
*
         
prevents it from being added to this collection
     
* @throws NullPointerException if the specified element is null and this
     
*
         
collection does not permit null elements
     
* @throws IllegalArgumentException if some property of the element
     
*
         
prevents it from being added to this collection
     
* @throws IllegalStateException if the element cannot be added at this
     
*
         
time due to insertion restrictions
     
*/

    
boolean add(E e);

    
/**
     
* Removes a single instance of the specified element from this
     
* collection, if it is present (optional operation).
  
More formally,
     
* removes an element <tt>e</tt> such that
     
* <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>, if
     
* this collection contains one or more such elements.
  
Returns
     
* <tt>true</tt> if this collection contained the specified element (or
     
* equivalently, if this collection changed as a result of the call).
     
*
     
* @param o element to be removed from this collection, if present
     
* @return <tt>true</tt> if an element was removed as a result of this call
     
* @throws ClassCastException if the type of the specified element
     
*
         
is incompatible with this collection
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
* @throws NullPointerException if the specified element is null and this
     
*
         
collection does not permit null elements
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
* @throws UnsupportedOperationException if the <tt>remove</tt> operation
     
*
         
is not supported by this collection
     
*/

    
boolean remove(Object o);


    
// Bulk Operations

    
/**
     
* Returns <tt>true</tt> if this collection contains all of the elements
     
* in the specified collection.
     
*
     
* @param
  
c collection to be checked for containment in this collection
     
* @return <tt>true</tt> if this collection contains all of the elements
     
*
         
in the specified collection
     
* @throws ClassCastException if the types of one or more elements
     
*
         
in the specified collection are incompatible with this
     
*
         
collection
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
* @throws NullPointerException if the specified collection contains one
     
*
         
or more null elements and this collection does not permit null
     
*
         
elements
     
*
         
(<a href="#optional-restrictions">optional</a>),
     
*
         
or if the specified collection is null.
     
* @see
    
#contains(Object)
     
*/

    
boolean containsAll(Collection<?> c);

    
/**
     
* Adds all of the elements in the specified collection to this collection
     
* (optional operation).
  
The behavior of this operation is undefined if
     
* the specified collection is modified while the operation is in progress.
     
* (This implies that the behavior of this call is undefined if the
     
* specified collection is this collection, and this collection is
     
* nonempty.)
     
*
     
* @param c collection containing elements to be added to this collection
     
* @return <tt>true</tt> if this collection changed as a result of the call
     
* @throws UnsupportedOperationException if the <tt>addAll</tt> operation
     
*
         
is not supported by this collection
     
* @throws ClassCastException if the class of an element of the specified
     
*
         
collection prevents it from being added to this collection
     
* @throws NullPointerException if the specified collection contains a
     
*
         
null element and this collection does not permit null elements,
     
*
         
or if the specified collection is null
     
* @throws IllegalArgumentException if some property of an element of the
     
*
         
specified collection prevents it from being added to this
     
*
         
collection
     
* @throws IllegalStateException if not all the elements can be added at
     
*
         
this time due to insertion restrictions
     
* @see #add(Object)
     
*/

    
boolean addAll(Collection<? extends E> c);

    
/**
     
* Removes all of this collection's elements that are also contained in the
     
* specified collection (optional operation).
  
After this call returns,
     
* this collection will contain no elements in common with the specified
     
* collection.
     
*
     
* @param c collection containing elements to be removed from this collection
     
* @return <tt>true</tt> if this collection changed as a result of the
     
*
         
call
     
* @throws UnsupportedOperationException if the <tt>removeAll</tt> method
     
*
         
is not supported by this collection
     
* @throws ClassCastException if the types of one or more elements
     
*
         
in this collection are incompatible with the specified
     
*
         
collection
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
* @throws NullPointerException if this collection contains one or more
     
*
         
null elements and the specified collection does not support
     
*
         
null elements
     
*
         
(<a href="#optional-restrictions">optional</a>),
     
*
         
or if the specified collection is null
     
* @see #remove(Object)
     
* @see #contains(Object)
     
*/

    
boolean removeAll(Collection<?> c);

    
/**
     
* Removes all of the elements of this collection that satisfy the given
     
* predicate.
  
Errors or runtime exceptions thrown during iteration or by
     
* the predicate are relayed to the caller.
     
*
     
* @implSpec
     
* The default implementation traverses all elements of the collection using
     
* its {@link #iterator}.
  
Each matching element is removed using
     
* {@link Iterator#remove()}.
  
If the collection's iterator does not
     
* support removal then an {@code UnsupportedOperationException} will be
     
* thrown on the first matching element.
     
*
     
* @param filter a predicate which returns {@code true} for elements to be
     
*
        
removed
     
* @return {@code true} if any elements were removed
     
* @throws NullPointerException if the specified filter is null
     
* @throws UnsupportedOperationException if elements cannot be removed
     
*
         
from this collection.
  
Implementations may throw this exception if a
     
*
         
matching element cannot be removed or if, in general, removal is not
     
*
         
supported.
     
* @since 1.8
     
*/

    
default boolean removeIf(Predicate<? super E> filter) {
        
Objects.requireNonNull(filter);
        
boolean removed = false;
        
final Iterator<E> each = iterator();
        
while (each.hasNext()) {
            
if (filter.test(each.next())) {
                
each.remove();
                
removed = true;
            
}
        
}
        
return removed;
    
}

    
/**
     
* Retains only the elements in this collection that are contained in the
     
* specified collection (optional operation).
  
In other words, removes from
     
* this collection all of its elements that are not contained in the
     
* specified collection.
     
*
     
* @param c collection containing elements to be retained in this collection
     
* @return <tt>true</tt> if this collection changed as a result of the call
     
* @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
     
*
         
is not supported by this collection
     
* @throws ClassCastException if the types of one or more elements
     
*
         
in this collection are incompatible with the specified
     
*
         
collection
     
*
         
(<a href="#optional-restrictions">optional</a>)
     
* @throws NullPointerException if this collection contains one or more
     
*
         
null elements and the specified collection does not permit null
     
*
         
elements
     
*
         
(<a href="#optional-restrictions">optional</a>),
     
*
         
or if the specified collection is null
     
* @see #remove(Object)
     
* @see #contains(Object)
     
*/

    
boolean retainAll(Collection<?> c);

    
/**
     
* Removes all of the elements from this collection (optional operation).
     
* The collection will be empty after this method returns.
     
*
     
* @throws UnsupportedOperationException if the <tt>clear</tt> operation
     
*
         
is not supported by this collection
     
*/

    
void clear();


    
// Comparison and hashing

    
/**
     
* Compares the specified object with this collection for equality. <p>
     
*
     
* While the <tt>Collection</tt> interface adds no stipulations to the
     
* general contract for the <tt>Object.equals</tt>, programmers who
     
* implement the <tt>Collection</tt> interface "directly" (in other words,
     
* create a class that is a <tt>Collection</tt> but is not a <tt>Set</tt>
     
* or a <tt>List</tt>) must exercise care if they choose to override the
     
* <tt>Object.equals</tt>.
  
It is not necessary to do so, and the simplest
     
* course of action is to rely on <tt>Object</tt>'s implementation, but
     
* the implementor may wish to implement a "value comparison" in place of
     
* the default "reference comparison."
  
(The <tt>List</tt> and
     
* <tt>Set</tt> interfaces mandate such value comparisons.)<p>
     
*
     
* The general contract for the <tt>Object.equals</tt> method states that
     
* equals must be symmetric (in other words, <tt>a.equals(b)</tt> if and
     
* only if <tt>b.equals(a)</tt>).
  
The contracts for <tt>List.equals</tt>
     
* and <tt>Set.equals</tt> state that lists are only equal to other lists,
     
* and sets to other sets.
  
Thus, a custom <tt>equals</tt> method for a
     
* collection class that implements neither the <tt>List</tt> nor
     
* <tt>Set</tt> interface must return <tt>false</tt> when this collection
     
* is compared to any list or set.
  
(By the same logic, it is not possible
     
* to write a class that correctly implements both the <tt>Set</tt> and
     
* <tt>List</tt> interfaces.)
     
*
     
* @param o object to be compared for equality with this collection
     
* @return <tt>true</tt> if the specified object is equal to this
     
* collection
     
*
     
* @see Object#equals(Object)
     
* @see Set#equals(Object)
     
* @see List#equals(Object)
     
*/

    
boolean equals(Object o);

    
/**
     
* Returns the hash code value for this collection.
  
While the
     
* <tt>Collection</tt> interface adds no stipulations to the general
     
* contract for the <tt>Object.hashCode</tt> method, programmers should
     
* take note that any class that overrides the <tt>Object.equals</tt>
     
* method must also override the <tt>Object.hashCode</tt> method in order
     
* to satisfy the general contract for the <tt>Object.hashCode</tt> method.
     
* In particular, <tt>c1.equals(c2)</tt> implies that
     
* <tt>c1.hashCode()==c2.hashCode()</tt>.
     
*
     
* @return the hash code value for this collection
     
*
     
* @see Object#hashCode()
     
* @see Object#equals(Object)
     
*/

    
int hashCode();

    
/**
     
* Creates a {@link Spliterator} over the elements in this collection.
     
*
     
* Implementations should document characteristic values reported by the
     
* spliterator.
  
Such characteristic values are not required to be reported
     
* if the spliterator reports {@link Spliterator#SIZED} and this collection
     
* contains no elements.
     
*
     
* <p>The default implementation should be overridden by subclasses that
     
* can return a more efficient spliterator.
  
In order to
     
* preserve expected laziness behavior for the
 
 
and
     
*
 
} methods, spliterators should either have the
     
* characteristic of {@code IMMUTABLE} or {@code CONCURRENT}, or be
     
* <em><a href="Spliterator.html#binding">late-binding</a></em>.
     
* If none of these is practical, the overriding class should describe the
     
* spliterator's documented policy of binding and structural interference,
     
* and should override the
 
 
and {@link #parallelStream()}
     
* methods to create streams using a {@code Supplier} of the spliterator,
     
* as in:
     
* <pre>{@code
     
*Stream<E> s = StreamSupport.stream(() -> spliterator(), spliteratorCharacteristics)
     
* }</pre>
     
* <p>These requirements ensure that streams produced by the
     
*
 
 
and {@link #parallelStream()} methods will reflect the
     
* contents of the collection as of initiation of the terminal stream
     
* operation.
     
*
     
* @implSpec
     
* The default implementation creates a
     
* <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
     
* from the collections's {@code Iterator}.
  
The spliterator inherits the
     
* <em>fail-fast</em> properties of the collection's iterator.
     
* <p>
     
* The created {@code Spliterator} reports {@link Spliterator#SIZED}.
     
*
     
* @implNote
     
* The created {@code Spliterator} additionally reports
     
* {@link Spliterator#SUBSIZED}.
     
*
     
* <p>If a spliterator covers no elements then the reporting of additional
     
* characteristic values, beyond that of {@code SIZED} and {@code SUBSIZED},
     
* does not aid clients to control, specialize or simplify computation.
     
* However, this does enable shared use of an immutable and empty
     
* spliterator instance (see {@link Spliterators#emptySpliterator()}) for
     
* empty collections, and enables clients to determine if such a spliterator
     
* covers no elements.
     
*
     
* @return a {@code Spliterator} over the elements in this collection
     
* @since 1.8
     
*/

    
@Override
    
default Spliterator<E> spliterator() {
        
return Spliterators.spliterator(this, 0);
    
}

    
/**
     
* Returns a sequential {@code Stream} with this collection as its source.
     
*
     
* <p>This method should be overridden when the
 

     
* method cannot return a spliterator that is {@code IMMUTABLE},
     
* {@code CONCURRENT}, or <em>late-binding</em>. (See
 

     
* for details.)
     
*
     
* @implSpec
     
* The default implementation creates a sequential {@code Stream} from the
     
* collection's {@code Spliterator}.
     
*
     
* @return a sequential {@code Stream} over the elements in this collection
     
* @since 1.8
     
*/

    
default Stream<E> stream() {
        
return StreamSupport.stream(spliterator(), false);
    
}

    
/**
     
* Returns a possibly parallel {@code Stream} with this collection as its
     
* source.
  
It is allowable for this method to return a sequential stream.
     
*
     
* <p>This method should be overridden when the
 

     
* method cannot return a spliterator that is {@code IMMUTABLE},
     
* {@code CONCURRENT}, or <em>late-binding</em>. (See
 

     
* for details.)
     
*
     
* @implSpec
     
* The default implementation creates a parallel {@code Stream} from the
     
* collection's {@code Spliterator}.
     
*
     
* @return a possibly parallel {@code Stream} over the elements in this
     
* collection
     
* @since 1.8
     
*/

    
default Stream<E> parallelStream() {
        
return StreamSupport.stream(spliterator(), true);
    
}
}