The ListIterator.java Java example source code
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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 {@code ListIterator}
* has no current element; its <I>cursor position always
* lies between the element that would be returned by a call
* to {@code previous()} and the element that would be
* returned by a call to {@code next()}.
* An iterator for a list of length {@code n} has {@code n+1} possible
* cursor positions, as illustrated by the carets ({@code ^}) below:
* <PRE>
* Element(0) Element(1) Element(2) ... Element(n-1)
* cursor positions: ^ ^ ^ ^ ^
* </PRE>
* Note that the {@link #remove} and {@link #set(Object)} methods are
* <i>not 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}/../technotes/guides/collections/index.html">
* Java Collections Framework</a>.
*
* @author Josh Bloch
* @see Collection
* @see List
* @see Iterator
* @see Enumeration
* @see List#listIterator()
* @since 1.2
*/
public interface ListIterator<E> extends Iterator {
// Query Operations
/**
* Returns {@code true} if this list iterator has more elements when
* traversing the list in the forward direction. (In other words,
* returns {@code true} if {@link #next} would return an element rather
* than throwing an exception.)
*
* @return {@code true} if the list iterator has more elements when
* traversing the list in the forward direction
*/
boolean hasNext();
/**
* Returns the next element in the list and advances the cursor position.
* This method may be called repeatedly to iterate through the list,
* or intermixed with calls to {@link #previous} to go back and forth.
* (Note that alternating calls to {@code next} and {@code previous}
* will return the same element repeatedly.)
*
* @return the next element in the list
* @throws NoSuchElementException if the iteration has no next element
*/
E next();
/**
* Returns {@code true} if this list iterator has more elements when
* traversing the list in the reverse direction. (In other words,
* returns {@code true} if {@link #previous} would return an element
* rather than throwing an exception.)
*
* @return {@code true} if the list iterator has more elements when
* traversing the list in the reverse direction
*/
boolean hasPrevious();
/**
* Returns the previous element in the list and moves the cursor
* position backwards. This method may be called repeatedly to
* iterate through the list backwards, or intermixed with calls to
* {@link #next} to go back and forth. (Note that alternating calls
* to {@code next} and {@code previous} will return the same
* element repeatedly.)
*
* @return the previous element in the list
* @throws 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 {@link #next}. (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 {@code next}, or list size if the list
* iterator is at the end of the list
*/
int nextIndex();
/**
* Returns the index of the element that would be returned by a
* subsequent call to {@link #previous}. (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 {@code previous}, or -1 if the list
* iterator is at the beginning of the list
*/
int previousIndex();
// Modification Operations
/**
* Removes from the list the last element that was returned by {@link
* #next} or {@link #previous} (optional operation). This call can
* only be made once per call to {@code next} or {@code previous}.
* It can be made only if {@link #add} has not been
* called after the last call to {@code next} or {@code previous}.
*
* @throws UnsupportedOperationException if the {@code remove}
* operation is not supported by this list iterator
* @throws IllegalStateException if neither {@code next} nor
* {@code previous} have been called, or {@code remove} or
* {@code add} have been called after the last call to
* {@code next} or {@code previous}
*/
void remove();
/**
* Replaces the last element returned by {@link #next} or
* {@link #previous} with the specified element (optional operation).
* This call can be made only if neither {@link #remove} nor {@link
* #add} have been called after the last call to {@code next} or
* {@code previous}.
*
* @param e the element with which to replace the last element returned by
* {@code next} or {@code previous}
* @throws UnsupportedOperationException if the {@code set} operation
* is not supported by this list iterator
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this list
* @throws IllegalArgumentException if some aspect of the specified
* element prevents it from being added to this list
* @throws IllegalStateException if neither {@code next} nor
* {@code previous} have been called, or {@code remove} or
* {@code add} have been called after the last call to
* {@code next} or {@code previous}
*/
void set(E e);
/**
* Inserts the specified element into the list (optional operation).
* The element is inserted immediately before the element that
* would be returned by {@link #next}, if any, and after the element
* that would be returned by {@link #previous}, 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 {@code next} would be unaffected, and a
* subsequent call to {@code previous} would return the new element.
* (This call increases by one the value that would be returned by a
* call to {@code nextIndex} or {@code previousIndex}.)
*
* @param e the element to insert
* @throws UnsupportedOperationException if the {@code add} method is
* not supported by this list iterator
* @throws ClassCastException if the class of the specified element
* prevents it from being added to this list
* @throws IllegalArgumentException if some aspect of this element
* prevents it from being added to this list
*/
void add(E e);
}
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