/*
 
* 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;

/**
 
* A collection that contains no duplicate elements.
  
More formally, sets
 
* contain no pair of elements <code>e1</code> and <code>e2</code> such that
 
* <code>e1.equals(e2)</code>, and at most one null element.
  
As implied by
 
* its name, this interface models the mathematical <i>set</i> abstraction.
 
*
 
* <p>The <tt>Set</tt> interface places additional stipulations, beyond those
 
* inherited from the <tt>Collection</tt> interface, on the contracts of all
 
* constructors and on the contracts of the <tt>add</tt>, <tt>equals</tt> and
 
* <tt>hashCode</tt> methods.
  
Declarations for other inherited methods are
 
* also included here for convenience.
  
(The specifications accompanying these
 
* declarations have been tailored to the <tt>Set</tt> interface, but they do
 
* not contain any additional stipulations.)
 
*
 
* <p>The additional stipulation on constructors is, not surprisingly,
 
* that all constructors must create a set that contains no duplicate elements
 
* (as defined above).
 
*
 
* <p>Note: Great care must be exercised if mutable objects are used as set
 
* elements.
  
The behavior of a set is not specified if the value of an object
 
* is changed in a manner that affects <tt>equals</tt> comparisons while the
 
* object is an element in the set.
  
A special case of this prohibition is
 
* that it is not permissible for a set to contain itself as an element.
 
*
 
* <p>Some set implementations have restrictions on the elements that
 
* they may contain.
  
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 set 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>This interface is a member of the
 
* <a href="{@docRoot}/../technotes/guides/collections/index.html">
 
* Java Collections Framework</a>.
 
*
 
* @param <E> the type of elements maintained by this set
 
*
 
* @author
  
Josh Bloch
 
* @author
  
Neal Gafter
 
* @see Collection
 
* @see List
 
* @see SortedSet
 
* @see HashSet
 
* @see TreeSet
 
* @see AbstractSet
 
* @see Collections#singleton(java.lang.Object)
 
* @see Collections#EMPTY_SET
 
* @since 1.2
 
*/


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

    
/**
     
* Returns the number of elements in this set (its cardinality).
  
If this
     
* set contains more than <tt>Integer.MAX_VALUE</tt> elements, returns
     
* <tt>Integer.MAX_VALUE</tt>.
     
*
     
* @return the number of elements in this set (its cardinality)
     
*/

    
int size();

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

    
boolean isEmpty();

    
/**
     
* Returns <tt>true</tt> if this set contains the specified element.
     
* More formally, returns <tt>true</tt> if and only if this set
     
* contains an 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 set is to be tested
     
* @return <tt>true</tt> if this set contains the specified element
     
* @throws ClassCastException if the type of the specified element
     
*
         
is incompatible with this set
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
* @throws NullPointerException if the specified element is null and this
     
*
         
set does not permit null elements
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
*/

    
boolean contains(Object o);

    
/**
     
* Returns an iterator over the elements in this set.
  
The elements are
     
* returned in no particular order (unless this set is an instance of some
     
* class that provides a guarantee).
     
*
     
* @return an iterator over the elements in this set
     
*/

    
Iterator<E> iterator();

    
/**
     
* Returns an array containing all of the elements in this set.
     
* If this set 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 set.
  
(In other words, this method must
     
* allocate a new array even if this set 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 the elements in this set
     
*/

    
Object[] toArray();

    
/**
     
* Returns an array containing all of the elements in this set; the
     
* runtime type of the returned array is that of the specified array.
     
* If the set 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 set.
     
*
     
* <p>If this set fits in the specified array with room to spare
     
* (i.e., the array has more elements than this set), the element in
     
* the array immediately following the end of the set is set to
     
* <tt>null</tt>.
  
(This is useful in determining the length of this
     
* set <i>only</i> if the caller knows that this set does not contain
     
* any null elements.)
     
*
     
* <p>If this set 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 set known to contain only strings.
     
* The following code can be used to dump the set 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 a the array into which the elements of this set 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 the elements in this set
     
* @throws ArrayStoreException if the runtime type of the specified array
     
*
         
is not a supertype of the runtime type of every element in this
     
*
         
set
     
* @throws NullPointerException if the specified array is null
     
*/

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


    
// Modification Operations

    
/**
     
* Adds the specified element to this set if it is not already present
     
* (optional operation).
  
More formally, adds the specified element
     
* <tt>e</tt> to this set if the set contains no element <tt>e2</tt>
     
* such that
     
* <tt>(e==null&nbsp;?&nbsp;e2==null&nbsp;:&nbsp;e.equals(e2))</tt>.
     
* If this set already contains the element, the call leaves the set
     
* unchanged and returns <tt>false</tt>.
  
In combination with the
     
* restriction on constructors, this ensures that sets never contain
     
* duplicate elements.
     
*
     
* <p>The stipulation above does not imply that sets must accept all
     
* elements; sets may refuse to add any particular element, including
     
* <tt>null</tt>, and throw an exception, as described in the
     
* specification for {@link Collection#add Collection.add}.
     
* Individual set implementations should clearly document any
     
* restrictions on the elements that they may contain.
     
*
     
* @param e element to be added to this set
     
* @return <tt>true</tt> if this set did not already contain the specified
     
*
         
element
     
* @throws UnsupportedOperationException if the <tt>add</tt> operation
     
*
         
is not supported by this set
     
* @throws ClassCastException if the class of the specified element
     
*
         
prevents it from being added to this set
     
* @throws NullPointerException if the specified element is null and this
     
*
         
set does not permit null elements
     
* @throws IllegalArgumentException if some property of the specified element
     
*
         
prevents it from being added to this set
     
*/

    
boolean add(E e);


    
/**
     
* Removes the specified element from this set 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 set contains such an element.
  
Returns <tt>true</tt> if this set
     
* contained the element (or equivalently, if this set changed as a
     
* result of the call).
  
(This set will not contain the element once the
     
* call returns.)
     
*
     
* @param o object to be removed from this set, if present
     
* @return <tt>true</tt> if this set contained the specified element
     
* @throws ClassCastException if the type of the specified element
     
*
         
is incompatible with this set
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
* @throws NullPointerException if the specified element is null and this
     
*
         
set does not permit null elements
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
* @throws UnsupportedOperationException if the <tt>remove</tt> operation
     
*
         
is not supported by this set
     
*/

    
boolean remove(Object o);


    
// Bulk Operations

    
/**
     
* Returns <tt>true</tt> if this set contains all of the elements of the
     
* specified collection.
  
If the specified collection is also a set, this
     
* method returns <tt>true</tt> if it is a <i>subset</i> of this set.
     
*
     
* @param
  
c collection to be checked for containment in this set
     
* @return <tt>true</tt> if this set contains all of the elements of the
     
*
         
specified collection
     
* @throws ClassCastException if the types of one or more elements
     
*
         
in the specified collection are incompatible with this
     
*
         
set
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
* @throws NullPointerException if the specified collection contains one
     
*
         
or more null elements and this set does not permit null
     
*
         
elements
     
* (<a href="Collection.html#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 set if
     
* they're not already present (optional operation).
  
If the specified
     
* collection is also a set, the <tt>addAll</tt> operation effectively
     
* modifies this set so that its value is the <i>union</i> of the two
     
* sets.
  
The behavior of this operation is undefined if the specified
     
* collection is modified while the operation is in progress.
     
*
     
* @param
  
c collection containing elements to be added to this set
     
* @return <tt>true</tt> if this set changed as a result of the call
     
*
     
* @throws UnsupportedOperationException if the <tt>addAll</tt> operation
     
*
         
is not supported by this set
     
* @throws ClassCastException if the class of an element of the
     
*
         
specified collection prevents it from being added to this set
     
* @throws NullPointerException if the specified collection contains one
     
*
         
or more null elements and this set 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 set
     
* @see #add(Object)
     
*/

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

    
/**
     
* Retains only the elements in this set that are contained in the
     
* specified collection (optional operation).
  
In other words, removes
     
* from this set all of its elements that are not contained in the
     
* specified collection.
  
If the specified collection is also a set, this
     
* operation effectively modifies this set so that its value is the
     
* <i>intersection</i> of the two sets.
     
*
     
* @param
  
c collection containing elements to be retained in this set
     
* @return <tt>true</tt> if this set changed as a result of the call
     
* @throws UnsupportedOperationException if the <tt>retainAll</tt> operation
     
*
         
is not supported by this set
     
* @throws ClassCastException if the class of an element of this set
     
*
         
is incompatible with the specified collection
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
* @throws NullPointerException if this set contains a null element and the
     
*
         
specified collection does not permit null elements
     
*
         
(<a href="Collection.html#optional-restrictions">optional</a>),
     
*
         
or if the specified collection is null
     
* @see #remove(Object)
     
*/

    
boolean retainAll(Collection<?> c);

    
/**
     
* Removes from this set all of its elements that are contained in the
     
* specified collection (optional operation).
  
If the specified
     
* collection is also a set, this operation effectively modifies this
     
* set so that its value is the <i>asymmetric set difference</i> of
     
* the two sets.
     
*
     
* @param
  
c collection containing elements to be removed from this set
     
* @return <tt>true</tt> if this set changed as a result of the call
     
* @throws UnsupportedOperationException if the <tt>removeAll</tt> operation
     
*
         
is not supported by this set
     
* @throws ClassCastException if the class of an element of this set
     
*
         
is incompatible with the specified collection
     
* (<a href="Collection.html#optional-restrictions">optional</a>)
     
* @throws NullPointerException if this set contains a null element and the
     
*
         
specified collection does not permit null elements
     
*
         
(<a href="Collection.html#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 from this set (optional operation).
     
* The set will be empty after this call returns.
     
*
     
* @throws UnsupportedOperationException if the <tt>clear</tt> method
     
*
         
is not supported by this set
     
*/

    
void clear();


    
// Comparison and hashing

    
/**
     
* Compares the specified object with this set for equality.
  
Returns
     
* <tt>true</tt> if the specified object is also a set, the two sets
     
* have the same size, and every member of the specified set is
     
* contained in this set (or equivalently, every member of this set is
     
* contained in the specified set).
  
This definition ensures that the
     
* equals method works properly across different implementations of the
     
* set interface.
     
*
     
* @param o object to be compared for equality with this set
     
* @return <tt>true</tt> if the specified object is equal to this set
     
*/

    
boolean equals(Object o);

    
/**
     
* Returns the hash code value for this set.
  
The hash code of a set is
     
* defined to be the sum of the hash codes of the elements in the set,
     
* where the hash code of a <tt>null</tt> element is defined to be zero.
     
* This ensures that <tt>s1.equals(s2)</tt> implies that
     
* <tt>s1.hashCode()==s2.hashCode()</tt> for any two sets <tt>s1</tt>
     
* and <tt>s2</tt>, as required by the general contract of
     
* {@link Object#hashCode}.
     
*
     
* @return the hash code value for this set
     
* @see Object#equals(Object)
     
* @see Set#equals(Object)
     
*/

    
int hashCode();

    
/**
     
* Creates a {@code Spliterator} over the elements in this set.
     
*
     
* <p>The {@code Spliterator} reports {@link Spliterator#DISTINCT}.
     
* Implementations should document the reporting of additional
     
* characteristic values.
     
*
     
* @implSpec
     
* The default implementation creates a
     
* <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator
     
* from the set's {@code Iterator}.
  
The spliterator inherits the
     
* <em>fail-fast</em> properties of the set's iterator.
     
* <p>
     
* The created {@code Spliterator} additionally reports
     
* {@link Spliterator#SIZED}.
     
*
     
* @implNote
     
* The created {@code Spliterator} additionally reports
     
* {@link Spliterator#SUBSIZED}.
     
*
     
* @return a {@code Spliterator} over the elements in this set
     
* @since 1.8
     
*/

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