/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

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
 */
@SuppressWarnings("all")
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 {@link #toArray()} 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);
 }
}