/*
* @(#)ListIterator.java 1.23 03/12/19
*
* Copyright 2004 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.util;
/**
*
* An iterator for lists that allows the programmer
* to traverse the list in either direction, modify
* the list during iteration, and obtain the iterator's
* current position in the list. A <TT>ListIterator</TT>
* has no current element; its <I>cursor position</I> always
* lies between the element that would be returned by a call
* to <TT>previous()</TT> and the element that would be
* returned by a call to <TT>next()</TT>. In a list of
* length <TT>n</TT>, there are <TT>n+1</TT> valid
* index values, from <TT>0</TT> to <TT>n</TT>, inclusive.
* <PRE>
*
* Element(0) Element(1) Element(2) ... Element(n)
* ^ ^ ^ ^ ^
* Index: 0 1 2 3 n+1
*
* </PRE>
* <P>
* Note that the {@link #remove} and {@link #set(Object)} methods are
* <i>not</i> defined in terms of the cursor position; they are defined to
* operate on the last element returned by a call to {@link #next} or {@link
* #previous()}.
* <P>
* This interface is a member of the
* <a href="{@docRoot}/../guide/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @version 1.23, 12/19/03
* @see Collection
* @see List
* @see Iterator
* @see Enumeration
* @since 1.2
*/
public interface ListIterator<E> extends Iterator<E> {
// Query Operations
/**
* Returns <tt>true</tt> if this list iterator has more elements when
* traversing the list in the forward direction. (In other words, returns
* <tt>true</tt> if <tt>next</tt> would return an element rather than
* throwing an exception.)
*
* @return <tt>true</tt> if the list iterator has more elements when
* traversing the list in the forward direction.
*/
boolean hasNext();
/**
* Returns the next element in the list. This method may be called
* repeatedly to iterate through the list, or intermixed with calls to
* <tt>previous</tt> to go back and forth. (Note that alternating calls
* to <tt>next</tt> and <tt>previous</tt> will return the same element
* repeatedly.)
*
* @return the next element in the list.
* @exception NoSuchElementException if the iteration has no next element.
*/
E next();
/**
* Returns <tt>true</tt> if this list iterator has more elements when
* traversing the list in the reverse direction. (In other words, returns
* <tt>true</tt> if <tt>previous</tt> would return an element rather than
* throwing an exception.)
*
* @return <tt>true</tt> if the list iterator has more elements when
* traversing the list in the reverse direction.
*/
boolean hasPrevious();
/**
* Returns the previous element in the list. This method may be called
* repeatedly to iterate through the list backwards, or intermixed with
* calls to <tt>next</tt> to go back and forth. (Note that alternating
* calls to <tt>next</tt> and <tt>previous</tt> will return the same
* element repeatedly.)
*
* @return the previous element in the list.
*
* @exception NoSuchElementException if the iteration has no previous
* element.
*/
E previous();
/**
* Returns the index of the element that would be returned by a subsequent
* call to <tt>next</tt>. (Returns list size if the list iterator is at the
* end of the list.)
*
* @return the index of the element that would be returned by a subsequent
* call to <tt>next</tt>, or list size if list iterator is at end
* of list.
*/
int nextIndex();
/**
* Returns the index of the element that would be returned by a subsequent
* call to <tt>previous</tt>. (Returns -1 if the list iterator is at the
* beginning of the list.)
*
* @return the index of the element that would be returned by a subsequent
* call to <tt>previous</tt>, or -1 if list iterator is at
* beginning of list.
*/
int previousIndex();
// Modification Operations
/**
* Removes from the list the last element that was returned by
* <tt>next</tt> or <tt>previous</tt> (optional operation). This call can
* only be made once per call to <tt>next</tt> or <tt>previous</tt>. It
* can be made only if <tt>ListIterator.add</tt> has not been called after
* the last call to <tt>next</tt> or <tt>previous</tt>.
*
* @exception UnsupportedOperationException if the <tt>remove</tt>
* operation is not supported by this list iterator.
* @exception IllegalStateException neither <tt>next</tt> nor
* <tt>previous</tt> have been called, or <tt>remove</tt> or
* <tt>add</tt> have been called after the last call to *
* <tt>next</tt> or <tt>previous</tt>.
*/
void remove();
/**
* Replaces the last element returned by <tt>next</tt> or
* <tt>previous</tt> with the specified element (optional operation).
* This call can be made only if neither <tt>ListIterator.remove</tt> nor
* <tt>ListIterator.add</tt> have been called after the last call to
* <tt>next</tt> or <tt>previous</tt>.
*
* @param o the element with which to replace the last element returned by
* <tt>next</tt> or <tt>previous</tt>.
* @exception UnsupportedOperationException if the <tt>set</tt> operation
* is not supported by this list iterator.
* @exception ClassCastException if the class of the specified element
* prevents it from being added to this list.
* @exception IllegalArgumentException if some aspect of the specified
* element prevents it from being added to this list.
* @exception IllegalStateException if neither <tt>next</tt> nor
* <tt>previous</tt> have been called, or <tt>remove</tt> or
* <tt>add</tt> have been called after the last call to
* <tt>next</tt> or <tt>previous</tt>.
*/
void set(E o);
/**
* Inserts the specified element into the list (optional operation). The
* element is inserted immediately before the next element that would be
* returned by <tt>next</tt>, if any, and after the next element that
* would be returned by <tt>previous</tt>, if any. (If the list contains
* no elements, the new element becomes the sole element on the list.)
* The new element is inserted before the implicit cursor: a subsequent
* call to <tt>next</tt> would be unaffected, and a subsequent call to
* <tt>previous</tt> would return the new element. (This call increases
* by one the value that would be returned by a call to <tt>nextIndex</tt>
* or <tt>previousIndex</tt>.)
*
* @param o the element to insert.
* @exception UnsupportedOperationException if the <tt>add</tt> method is
* not supported by this list iterator.
*
* @exception ClassCastException if the class of the specified element
* prevents it from being added to this list.
*
* @exception IllegalArgumentException if some aspect of this element
* prevents it from being added to this list.
*/
void add(E o);
}
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