244 lines
8.9 KiB
Java
244 lines
8.9 KiB
Java
/* Set.java -- A collection that prohibits duplicates
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Copyright (C) 1998, 2001 Free Software Foundation, Inc.
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This file is part of GNU Classpath.
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GNU Classpath is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2, or (at your option)
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any later version.
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GNU Classpath is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with GNU Classpath; see the file COPYING. If not, write to the
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Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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02111-1307 USA.
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Linking this library statically or dynamically with other modules is
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making a combined work based on this library. Thus, the terms and
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conditions of the GNU General Public License cover the whole
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combination.
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As a special exception, the copyright holders of this library give you
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permission to link this library with independent modules to produce an
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executable, regardless of the license terms of these independent
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modules, and to copy and distribute the resulting executable under
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terms of your choice, provided that you also meet, for each linked
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independent module, the terms and conditions of the license of that
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module. An independent module is a module which is not derived from
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or based on this library. If you modify this library, you may extend
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this exception to your version of the library, but you are not
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obligated to do so. If you do not wish to do so, delete this
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exception statement from your version. */
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package java.util;
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/**
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* A collection that contains no duplicates. In other words, for two set
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* elements e1 and e2, <code>e1.equals(e2)</code> returns false. There
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* are additional stipulations on <code>add</code>, <code>equals</code>
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* and <code>hashCode</code>, as well as the requirements that constructors
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* do not permit duplicate elements. The Set interface is incompatible with
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* List; you cannot implement both simultaneously.
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* <p>
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*
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* Note: Be careful about using mutable objects in sets. In particular,
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* if a mutable object changes to become equal to another set element, you
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* have violated the contract. As a special case of this, a Set is not
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* allowed to be an element of itself, without risking undefined behavior.
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*
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* @author Original author unknown
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* @author Eric Blake <ebb9@email.byu.edu>
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* @see Collection
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* @see List
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* @see SortedSet
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* @see HashSet
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* @see TreeSet
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* @see LinkedHashSet
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* @see AbstractSet
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* @see Collections#singleton(Object)
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* @see Collections#EMPTY_SET
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* @since 1.2
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* @status updated to 1.4
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*/
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public interface Set extends Collection
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{
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/**
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* Adds the specified element to the set if it is not already present
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* (optional operation). In particular, the comparison algorithm is
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* <code>o == null ? e == null : o.equals(e)</code>. Sets need not permit
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* all values, and may document what exceptions will be thrown if
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* a value is not permitted.
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*
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* @param o the object to add
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* @return true if the object was not previously in the set
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* @throws UnsupportedOperationException if this operation is not allowed
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* @throws ClassCastException if the class of o prevents it from being added
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* @throws IllegalArgumentException if some aspect of o prevents it from
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* being added
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* @throws NullPointerException if null is not permitted in this set
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*/
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boolean add(Object o);
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/**
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* Adds all of the elements of the given collection to this set (optional
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* operation). If the argument is also a Set, this returns the mathematical
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* <i>union</i> of the two. The behavior is unspecified if the set is
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* modified while this is taking place.
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*
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* @param c the collection to add
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* @return true if the set changed as a result
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* @throws UnsupportedOperationException if this operation is not allowed
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* @throws ClassCastException if the class of an element prevents it from
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* being added
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* @throws IllegalArgumentException if something about an element prevents
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* it from being added
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* @throws NullPointerException if null is not permitted in this set, or
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* if the argument c is null
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* @see #add(Object)
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*/
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boolean addAll(Collection c);
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/**
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* Removes all elements from this set (optional operation). This set will
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* be empty afterwords, unless an exception occurs.
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*
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* @throws UnsupportedOperationException if this operation is not allowed
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*/
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void clear();
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/**
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* Returns true if the set contains the specified element. In other words,
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* this looks for <code>o == null ? e == null : o.equals(e)</code>.
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*
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* @param o the object to look for
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* @return true if it is found in the set
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*/
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boolean contains(Object o);
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/**
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* Returns true if this set contains all elements in the specified
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* collection. If the argument is also a set, this is the <i>subset</i>
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* relationship.
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*
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* @param c the collection to check membership in
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* @return true if all elements in this set are in c
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* @throws NullPointerException if c is null
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* @see #contains(Object)
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*/
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boolean containsAll(Collection c);
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/**
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* Compares the specified object to this for equality. For sets, the object
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* must be a set, the two must have the same size, and every element in
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* one must be in the other.
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*
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* @param o the object to compare to
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* @return true if it is an equal set
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*/
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boolean equals(Object o);
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/**
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* Returns the hash code for this set. In order to satisfy the contract of
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* equals, this is the sum of the hashcode of all elements in the set.
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*
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* @return the sum of the hashcodes of all set elements
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*/
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int hashCode();
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/**
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* Returns true if the set contains no elements.
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*
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* @return true if the set is empty
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*/
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boolean isEmpty();
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/**
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* Returns an iterator over the set. The iterator has no specific order,
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* unless further specified.
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*
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* @return a set iterator
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*/
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Iterator iterator();
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/**
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* Removes the specified element from this set (optional operation). If
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* an element e exists, <code>o == null ? e == null : o.equals(e)</code>,
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* it is removed from the set.
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*
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* @param o the object to remove
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* @return true if the set changed (an object was removed)
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* @throws UnsupportedOperationException if this operation is not allowed
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*/
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boolean remove(Object o);
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/**
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* Removes from this set all elements contained in the specified collection
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* (optional operation). If the argument is a set, this returns the
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* <i>asymmetric set difference</i> of the two sets.
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*
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* @param c the collection to remove from this set
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* @return true if this set changed as a result
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* @throws UnsupportedOperationException if this operation is not allowed
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* @throws NullPointerException if c is null
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* @see #remove(Object)
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*/
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boolean removeAll(Collection c);
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/**
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* Retains only the elements in this set that are also in the specified
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* collection (optional operation). If the argument is also a set, this
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* performs the <i>intersection</i> of the two sets.
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*
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* @param c the collection to keep
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* @return true if this set was modified
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* @throws UnsupportedOperationException if this operation is not allowed
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* @throws NullPointerException if c is null
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* @see #remove(Object)
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*/
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boolean retainAll(Collection c);
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/**
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* Returns the number of elements in the set. If there are more
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* than Integer.MAX_VALUE mappings, return Integer.MAX_VALUE. This is
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* the <i>cardinality</i> of the set.
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*
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* @return the number of elements
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*/
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int size();
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/**
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* Returns an array containing the elements of this set. If the set
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* makes a guarantee about iteration order, the array has the same
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* order. The array is distinct from the set; modifying one does not
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* affect the other.
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*
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* @return an array of this set's elements
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* @see #toArray(Object[])
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*/
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Object[] toArray();
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/**
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* Returns an array containing the elements of this set, of the same runtime
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* type of the argument. If the given set is large enough, it is reused,
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* and null is inserted in the first unused slot. Otherwise, reflection
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* is used to build a new array. If the set makes a guarantee about iteration
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* order, the array has the same order. The array is distinct from the set;
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* modifying one does not affect the other.
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*
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* @param a the array to determine the return type; if it is big enough
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* it is used and returned
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* @return an array holding the elements of the set
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* @throws ArrayStoreException if the runtime type of a is not a supertype
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* of all elements in the set
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* @throws NullPointerException if a is null
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* @see #toArray()
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*/
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Object[] toArray(Object[] a);
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}
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