jaroslav@557: /* jaroslav@557: * Copyright (c) 1997, 2006, Oracle and/or its affiliates. All rights reserved. jaroslav@557: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. jaroslav@557: * jaroslav@557: * This code is free software; you can redistribute it and/or modify it jaroslav@557: * under the terms of the GNU General Public License version 2 only, as jaroslav@557: * published by the Free Software Foundation. Oracle designates this jaroslav@557: * particular file as subject to the "Classpath" exception as provided jaroslav@557: * by Oracle in the LICENSE file that accompanied this code. jaroslav@557: * jaroslav@557: * This code is distributed in the hope that it will be useful, but WITHOUT jaroslav@557: * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or jaroslav@557: * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License jaroslav@557: * version 2 for more details (a copy is included in the LICENSE file that jaroslav@557: * accompanied this code). jaroslav@557: * jaroslav@557: * You should have received a copy of the GNU General Public License version jaroslav@557: * 2 along with this work; if not, write to the Free Software Foundation, jaroslav@557: * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. jaroslav@557: * jaroslav@557: * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA jaroslav@557: * or visit www.oracle.com if you need additional information or have any jaroslav@557: * questions. jaroslav@557: */ jaroslav@557: jaroslav@557: package java.util; jaroslav@557: jaroslav@557: /** jaroslav@557: * A collection that contains no duplicate elements. More formally, sets jaroslav@557: * contain no pair of elements e1 and e2 such that jaroslav@557: * e1.equals(e2), and at most one null element. As implied by jaroslav@557: * its name, this interface models the mathematical set abstraction. jaroslav@557: * jaroslav@557: *

The Set interface places additional stipulations, beyond those jaroslav@557: * inherited from the Collection interface, on the contracts of all jaroslav@557: * constructors and on the contracts of the add, equals and jaroslav@557: * hashCode methods. Declarations for other inherited methods are jaroslav@557: * also included here for convenience. (The specifications accompanying these jaroslav@557: * declarations have been tailored to the Set interface, but they do jaroslav@557: * not contain any additional stipulations.) jaroslav@557: * jaroslav@557: *

The additional stipulation on constructors is, not surprisingly, jaroslav@557: * that all constructors must create a set that contains no duplicate elements jaroslav@557: * (as defined above). jaroslav@557: * jaroslav@557: *

Note: Great care must be exercised if mutable objects are used as set jaroslav@557: * elements. The behavior of a set is not specified if the value of an object jaroslav@557: * is changed in a manner that affects equals comparisons while the jaroslav@557: * object is an element in the set. A special case of this prohibition is jaroslav@557: * that it is not permissible for a set to contain itself as an element. jaroslav@557: * jaroslav@557: *

Some set implementations have restrictions on the elements that jaroslav@557: * they may contain. For example, some implementations prohibit null elements, jaroslav@557: * and some have restrictions on the types of their elements. Attempting to jaroslav@557: * add an ineligible element throws an unchecked exception, typically jaroslav@557: * NullPointerException or ClassCastException. Attempting jaroslav@557: * to query the presence of an ineligible element may throw an exception, jaroslav@557: * or it may simply return false; some implementations will exhibit the former jaroslav@557: * behavior and some will exhibit the latter. More generally, attempting an jaroslav@557: * operation on an ineligible element whose completion would not result in jaroslav@557: * the insertion of an ineligible element into the set may throw an jaroslav@557: * exception or it may succeed, at the option of the implementation. jaroslav@557: * Such exceptions are marked as "optional" in the specification for this jaroslav@557: * interface. jaroslav@557: * jaroslav@557: *

This interface is a member of the jaroslav@557: * jaroslav@557: * Java Collections Framework. jaroslav@557: * jaroslav@557: * @param the type of elements maintained by this set jaroslav@557: * jaroslav@557: * @author Josh Bloch jaroslav@557: * @author Neal Gafter jaroslav@557: * @see Collection jaroslav@557: * @see List jaroslav@557: * @see SortedSet jaroslav@557: * @see HashSet jaroslav@557: * @see TreeSet jaroslav@557: * @see AbstractSet jaroslav@557: * @see Collections#singleton(java.lang.Object) jaroslav@557: * @see Collections#EMPTY_SET jaroslav@557: * @since 1.2 jaroslav@557: */ jaroslav@557: jaroslav@557: public interface Set extends Collection { jaroslav@557: // Query Operations jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns the number of elements in this set (its cardinality). If this jaroslav@557: * set contains more than Integer.MAX_VALUE elements, returns jaroslav@557: * Integer.MAX_VALUE. jaroslav@557: * jaroslav@557: * @return the number of elements in this set (its cardinality) jaroslav@557: */ jaroslav@557: int size(); jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns true if this set contains no elements. jaroslav@557: * jaroslav@557: * @return true if this set contains no elements jaroslav@557: */ jaroslav@557: boolean isEmpty(); jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns true if this set contains the specified element. jaroslav@557: * More formally, returns true if and only if this set jaroslav@557: * contains an element e such that jaroslav@557: * (o==null ? e==null : o.equals(e)). jaroslav@557: * jaroslav@557: * @param o element whose presence in this set is to be tested jaroslav@557: * @return true if this set contains the specified element jaroslav@557: * @throws ClassCastException if the type of the specified element jaroslav@557: * is incompatible with this set jaroslav@557: * (optional) jaroslav@557: * @throws NullPointerException if the specified element is null and this jaroslav@557: * set does not permit null elements jaroslav@557: * (optional) jaroslav@557: */ jaroslav@557: boolean contains(Object o); jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns an iterator over the elements in this set. The elements are jaroslav@557: * returned in no particular order (unless this set is an instance of some jaroslav@557: * class that provides a guarantee). jaroslav@557: * jaroslav@557: * @return an iterator over the elements in this set jaroslav@557: */ jaroslav@557: Iterator iterator(); jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns an array containing all of the elements in this set. jaroslav@557: * If this set makes any guarantees as to what order its elements jaroslav@557: * are returned by its iterator, this method must return the jaroslav@557: * elements in the same order. jaroslav@557: * jaroslav@557: *

The returned array will be "safe" in that no references to it jaroslav@557: * are maintained by this set. (In other words, this method must jaroslav@557: * allocate a new array even if this set is backed by an array). jaroslav@557: * The caller is thus free to modify the returned array. jaroslav@557: * jaroslav@557: *

This method acts as bridge between array-based and collection-based jaroslav@557: * APIs. jaroslav@557: * jaroslav@557: * @return an array containing all the elements in this set jaroslav@557: */ jaroslav@557: Object[] toArray(); jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns an array containing all of the elements in this set; the jaroslav@557: * runtime type of the returned array is that of the specified array. jaroslav@557: * If the set fits in the specified array, it is returned therein. jaroslav@557: * Otherwise, a new array is allocated with the runtime type of the jaroslav@557: * specified array and the size of this set. jaroslav@557: * jaroslav@557: *

If this set fits in the specified array with room to spare jaroslav@557: * (i.e., the array has more elements than this set), the element in jaroslav@557: * the array immediately following the end of the set is set to jaroslav@557: * null. (This is useful in determining the length of this jaroslav@557: * set only if the caller knows that this set does not contain jaroslav@557: * any null elements.) jaroslav@557: * jaroslav@557: *

If this set makes any guarantees as to what order its elements jaroslav@557: * are returned by its iterator, this method must return the elements jaroslav@557: * in the same order. jaroslav@557: * jaroslav@557: *

Like the {@link #toArray()} method, this method acts as bridge between jaroslav@557: * array-based and collection-based APIs. Further, this method allows jaroslav@557: * precise control over the runtime type of the output array, and may, jaroslav@557: * under certain circumstances, be used to save allocation costs. jaroslav@557: * jaroslav@557: *

Suppose x is a set known to contain only strings. jaroslav@557: * The following code can be used to dump the set into a newly allocated jaroslav@557: * array of String: jaroslav@557: * jaroslav@557: * 

jaroslav@557:      *     String[] y = x.toArray(new String[0]);
jaroslav@557: * jaroslav@557: * Note that toArray(new Object[0]) is identical in function to jaroslav@557: * toArray(). jaroslav@557: * jaroslav@557: * @param a the array into which the elements of this set are to be jaroslav@557: * stored, if it is big enough; otherwise, a new array of the same jaroslav@557: * runtime type is allocated for this purpose. jaroslav@557: * @return an array containing all the elements in this set jaroslav@557: * @throws ArrayStoreException if the runtime type of the specified array jaroslav@557: * is not a supertype of the runtime type of every element in this jaroslav@557: * set jaroslav@557: * @throws NullPointerException if the specified array is null jaroslav@557: */ jaroslav@557: T[] toArray(T[] a); jaroslav@557: jaroslav@557: jaroslav@557: // Modification Operations jaroslav@557: jaroslav@557: /** jaroslav@557: * Adds the specified element to this set if it is not already present jaroslav@557: * (optional operation). More formally, adds the specified element jaroslav@557: * e to this set if the set contains no element e2 jaroslav@557: * such that jaroslav@557: * (e==null ? e2==null : e.equals(e2)). jaroslav@557: * If this set already contains the element, the call leaves the set jaroslav@557: * unchanged and returns false. In combination with the jaroslav@557: * restriction on constructors, this ensures that sets never contain jaroslav@557: * duplicate elements. jaroslav@557: * jaroslav@557: *

The stipulation above does not imply that sets must accept all jaroslav@557: * elements; sets may refuse to add any particular element, including jaroslav@557: * null, and throw an exception, as described in the jaroslav@557: * specification for {@link Collection#add Collection.add}. jaroslav@557: * Individual set implementations should clearly document any jaroslav@557: * restrictions on the elements that they may contain. jaroslav@557: * jaroslav@557: * @param e element to be added to this set jaroslav@557: * @return true if this set did not already contain the specified jaroslav@557: * element jaroslav@557: * @throws UnsupportedOperationException if the add operation jaroslav@557: * is not supported by this set jaroslav@557: * @throws ClassCastException if the class of the specified element jaroslav@557: * prevents it from being added to this set jaroslav@557: * @throws NullPointerException if the specified element is null and this jaroslav@557: * set does not permit null elements jaroslav@557: * @throws IllegalArgumentException if some property of the specified element jaroslav@557: * prevents it from being added to this set jaroslav@557: */ jaroslav@557: boolean add(E e); jaroslav@557: jaroslav@557: jaroslav@557: /** jaroslav@557: * Removes the specified element from this set if it is present jaroslav@557: * (optional operation). More formally, removes an element e jaroslav@557: * such that jaroslav@557: * (o==null ? e==null : o.equals(e)), if jaroslav@557: * this set contains such an element. Returns true if this set jaroslav@557: * contained the element (or equivalently, if this set changed as a jaroslav@557: * result of the call). (This set will not contain the element once the jaroslav@557: * call returns.) jaroslav@557: * jaroslav@557: * @param o object to be removed from this set, if present jaroslav@557: * @return true if this set contained the specified element jaroslav@557: * @throws ClassCastException if the type of the specified element jaroslav@557: * is incompatible with this set jaroslav@557: * (optional) jaroslav@557: * @throws NullPointerException if the specified element is null and this jaroslav@557: * set does not permit null elements jaroslav@557: * (optional) jaroslav@557: * @throws UnsupportedOperationException if the remove operation jaroslav@557: * is not supported by this set jaroslav@557: */ jaroslav@557: boolean remove(Object o); jaroslav@557: jaroslav@557: jaroslav@557: // Bulk Operations jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns true if this set contains all of the elements of the jaroslav@557: * specified collection. If the specified collection is also a set, this jaroslav@557: * method returns true if it is a subset of this set. jaroslav@557: * jaroslav@557: * @param c collection to be checked for containment in this set jaroslav@557: * @return true if this set contains all of the elements of the jaroslav@557: * specified collection jaroslav@557: * @throws ClassCastException if the types of one or more elements jaroslav@557: * in the specified collection are incompatible with this jaroslav@557: * set jaroslav@557: * (optional) jaroslav@557: * @throws NullPointerException if the specified collection contains one jaroslav@557: * or more null elements and this set does not permit null jaroslav@557: * elements jaroslav@557: * (optional), jaroslav@557: * or if the specified collection is null jaroslav@557: * @see #contains(Object) jaroslav@557: */ jaroslav@557: boolean containsAll(Collection c); jaroslav@557: jaroslav@557: /** jaroslav@557: * Adds all of the elements in the specified collection to this set if jaroslav@557: * they're not already present (optional operation). If the specified jaroslav@557: * collection is also a set, the addAll operation effectively jaroslav@557: * modifies this set so that its value is the union of the two jaroslav@557: * sets. The behavior of this operation is undefined if the specified jaroslav@557: * collection is modified while the operation is in progress. jaroslav@557: * jaroslav@557: * @param c collection containing elements to be added to this set jaroslav@557: * @return true if this set changed as a result of the call jaroslav@557: * jaroslav@557: * @throws UnsupportedOperationException if the addAll operation jaroslav@557: * is not supported by this set jaroslav@557: * @throws ClassCastException if the class of an element of the jaroslav@557: * specified collection prevents it from being added to this set jaroslav@557: * @throws NullPointerException if the specified collection contains one jaroslav@557: * or more null elements and this set does not permit null jaroslav@557: * elements, or if the specified collection is null jaroslav@557: * @throws IllegalArgumentException if some property of an element of the jaroslav@557: * specified collection prevents it from being added to this set jaroslav@557: * @see #add(Object) jaroslav@557: */ jaroslav@557: boolean addAll(Collection c); jaroslav@557: jaroslav@557: /** jaroslav@557: * Retains only the elements in this set that are contained in the jaroslav@557: * specified collection (optional operation). In other words, removes jaroslav@557: * from this set all of its elements that are not contained in the jaroslav@557: * specified collection. If the specified collection is also a set, this jaroslav@557: * operation effectively modifies this set so that its value is the jaroslav@557: * intersection of the two sets. jaroslav@557: * jaroslav@557: * @param c collection containing elements to be retained in this set jaroslav@557: * @return true if this set changed as a result of the call jaroslav@557: * @throws UnsupportedOperationException if the retainAll operation jaroslav@557: * is not supported by this set jaroslav@557: * @throws ClassCastException if the class of an element of this set jaroslav@557: * is incompatible with the specified collection jaroslav@557: * (optional) jaroslav@557: * @throws NullPointerException if this set contains a null element and the jaroslav@557: * specified collection does not permit null elements jaroslav@557: * (optional), jaroslav@557: * or if the specified collection is null jaroslav@557: * @see #remove(Object) jaroslav@557: */ jaroslav@557: boolean retainAll(Collection c); jaroslav@557: jaroslav@557: /** jaroslav@557: * Removes from this set all of its elements that are contained in the jaroslav@557: * specified collection (optional operation). If the specified jaroslav@557: * collection is also a set, this operation effectively modifies this jaroslav@557: * set so that its value is the asymmetric set difference of jaroslav@557: * the two sets. jaroslav@557: * jaroslav@557: * @param c collection containing elements to be removed from this set jaroslav@557: * @return true if this set changed as a result of the call jaroslav@557: * @throws UnsupportedOperationException if the removeAll operation jaroslav@557: * is not supported by this set jaroslav@557: * @throws ClassCastException if the class of an element of this set jaroslav@557: * is incompatible with the specified collection jaroslav@557: * (optional) jaroslav@557: * @throws NullPointerException if this set contains a null element and the jaroslav@557: * specified collection does not permit null elements jaroslav@557: * (optional), jaroslav@557: * or if the specified collection is null jaroslav@557: * @see #remove(Object) jaroslav@557: * @see #contains(Object) jaroslav@557: */ jaroslav@557: boolean removeAll(Collection c); jaroslav@557: jaroslav@557: /** jaroslav@557: * Removes all of the elements from this set (optional operation). jaroslav@557: * The set will be empty after this call returns. jaroslav@557: * jaroslav@557: * @throws UnsupportedOperationException if the clear method jaroslav@557: * is not supported by this set jaroslav@557: */ jaroslav@557: void clear(); jaroslav@557: jaroslav@557: jaroslav@557: // Comparison and hashing jaroslav@557: jaroslav@557: /** jaroslav@557: * Compares the specified object with this set for equality. Returns jaroslav@557: * true if the specified object is also a set, the two sets jaroslav@557: * have the same size, and every member of the specified set is jaroslav@557: * contained in this set (or equivalently, every member of this set is jaroslav@557: * contained in the specified set). This definition ensures that the jaroslav@557: * equals method works properly across different implementations of the jaroslav@557: * set interface. jaroslav@557: * jaroslav@557: * @param o object to be compared for equality with this set jaroslav@557: * @return true if the specified object is equal to this set jaroslav@557: */ jaroslav@557: boolean equals(Object o); jaroslav@557: jaroslav@557: /** jaroslav@557: * Returns the hash code value for this set. The hash code of a set is jaroslav@557: * defined to be the sum of the hash codes of the elements in the set, jaroslav@557: * where the hash code of a null element is defined to be zero. jaroslav@557: * This ensures that s1.equals(s2) implies that jaroslav@557: * s1.hashCode()==s2.hashCode() for any two sets s1 jaroslav@557: * and s2, as required by the general contract of jaroslav@557: * {@link Object#hashCode}. jaroslav@557: * jaroslav@557: * @return the hash code value for this set jaroslav@557: * @see Object#equals(Object) jaroslav@557: * @see Set#equals(Object) jaroslav@557: */ jaroslav@557: int hashCode(); jaroslav@557: }