171 lines
6.7 KiB
Java
171 lines
6.7 KiB
Java
/* ListIterator.java -- Extended Iterator for iterating over ordered lists
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Copyright (C) 1998, 1999, 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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* An extended version of Iterator to support the extra features of Lists. The
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* elements may be accessed in forward or reverse order, elements may be
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* replaced as well as removed, and new elements may be inserted, during the
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* traversal of the list.
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* <p>
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*
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* A list with n elements provides n+1 iterator positions (the front, the end,
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* or between two elements). Note that <code>remove</code> and <code>set</code>
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* operate on the last element returned, whether it was by <code>next</code>
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* or <code>previous</code>.
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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 Iterator
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* @see Enumeration
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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 ListIterator extends Iterator
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{
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/**
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* Tests whether there are elements remaining in the list in the forward
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* direction. In other words, next() will not fail with a
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* NoSuchElementException.
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*
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* @return true if the list continues in the forward direction
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*/
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boolean hasNext();
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/**
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* Tests whether there are elements remaining in the list in the reverse
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* direction. In other words, previous() will not fail with a
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* NoSuchElementException.
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*
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* @return true if the list continues in the reverse direction
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*/
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boolean hasPrevious();
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/**
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* Obtain the next element in the list in the forward direction. Repeated
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* calls to next may be used to iterate over the entire list, or calls to
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* next and previous may be used together to go forwards and backwards.
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* Alternating calls to next and previous will return the same element.
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*
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* @return the next element in the list in the forward direction
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* @throws NoSuchElementException if there are no more elements
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*/
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Object next();
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/**
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* Obtain the next element in the list in the reverse direction. Repeated
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* calls to previous may be used to iterate backwards over the entire list,
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* or calls to next and previous may be used together to go forwards and
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* backwards. Alternating calls to next and previous will return the same
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* element.
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*
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* @return the next element in the list in the reverse direction
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* @throws NoSuchElementException if there are no more elements
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*/
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Object previous();
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/**
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* Find the index of the element that would be returned by a call to next.
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* If hasNext() returns false, this returns the list size.
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*
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* @return the index of the element that would be returned by next()
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*/
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int nextIndex();
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/**
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* Find the index of the element that would be returned by a call to
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* previous. If hasPrevious() returns false, this returns -1.
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*
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* @return the index of the element that would be returned by previous()
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*/
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int previousIndex();
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/**
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* Insert an element into the list at the current position of the iterator
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* (optional operation). The element is inserted in between the element that
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* would be returned by previous and the element that would be returned by
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* next. After the insertion, a subsequent call to next is unaffected, but
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* a call to previous returns the item that was added. The values returned
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* by nextIndex() and previousIndex() are incremented.
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*
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* @param o the object to insert into the list
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* @throws ClassCastException the object is of a type which cannot be added
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* to this list
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* @throws IllegalArgumentException some other aspect of the object stops
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* it being added to this list
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* @throws UnsupportedOperationException if this ListIterator does not
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* support the add operation
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*/
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void add(Object o);
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/**
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* Remove from the list the element last returned by a call to next or
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* previous (optional operation). This method may only be called if neither
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* add nor remove have been called since the last call to next or previous.
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*
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* @throws IllegalStateException if neither next or previous have been
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* called, or if add or remove has been called since the last call
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* to next or previous
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* @throws UnsupportedOperationException if this ListIterator does not
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* support the remove operation
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*/
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void remove();
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/**
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* Replace the element last returned by a call to next or previous with a
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* given object (optional operation). This method may only be called if
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* neither add nor remove have been called since the last call to next or
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* previous.
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*
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* @param o the object to replace the element with
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* @throws ClassCastException the object is of a type which cannot be added
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* to this list
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* @throws IllegalArgumentException some other aspect of the object stops
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* it being added to this list
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* @throws IllegalStateException if neither next or previous have been
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* called, or if add or remove has been called since the last call
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* to next or previous
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* @throws UnsupportedOperationException if this ListIterator does not
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* support the set operation
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*/
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void set(Object o);
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}
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