| /* |
| * 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 |
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| * 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 ? e==null : 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 ? e2==null : 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 ? e==null : 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); |
| } |
| } |
