/*
 * @(#)AbstractSequentialList.java	1.36 06/04/21
 *
 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
 * SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 */

package java.util;

/**
 * This class provides a skeletal implementation of the <tt>List</tt>
 * interface to minimize the effort required to implement this interface
 * backed by a "sequential access" data store (such as a linked list).  For
 * random access data (such as an array), <tt>AbstractList</tt> should be used
 * in preference to this class.<p>
 *
 * This class is the opposite of the <tt>AbstractList</tt> class in the sense
 * that it implements the "random access" methods (<tt>get(int index)</tt>,
 * <tt>set(int index, E element)</tt>, <tt>add(int index, E element)</tt> and
 * <tt>remove(int index)</tt>) on top of the list's list iterator, instead of
 * the other way around.<p>
 *
 * To implement a list the programmer needs only to extend this class and
 * provide implementations for the <tt>listIterator</tt> and <tt>size</tt>
 * methods.  For an unmodifiable list, the programmer need only implement the
 * list iterator's <tt>hasNext</tt>, <tt>next</tt>, <tt>hasPrevious</tt>,
 * <tt>previous</tt> and <tt>index</tt> methods.<p>
 *
 * For a modifiable list the programmer should additionally implement the list
 * iterator's <tt>set</tt> method.  For a variable-size list the programmer
 * should additionally implement the list iterator's <tt>remove</tt> and
 * <tt>add</tt> methods.<p>
 *
 * The programmer should generally provide a void (no argument) and collection
 * constructor, as per the recommendation in the <tt>Collection</tt> interface
 * specification.<p>
 *
 * This class is a member of the
 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @author  Josh Bloch
 * @author  Neal Gafter
 * @version 1.36, 04/21/06
 * @see Collection
 * @see List
 * @see AbstractList
 * @see AbstractCollection
 * @since 1.2
 */

public abstract class AbstractSequentialList<E> extends AbstractList<E> {
    /**
     * Sole constructor.  (For invocation by subclass constructors, typically
     * implicit.)
     */
    protected AbstractSequentialList() {
    }

    /**
     * Returns the element at the specified position in this list.
     *
     * <p>This implementation first gets a list iterator pointing to the
     * indexed element (with <tt>listIterator(index)</tt>).  Then, it gets
     * the element using <tt>ListIterator.next</tt> and returns it.
     *
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public E get(int index) {
        try {
            return listIterator(index).next();
        } catch (NoSuchElementException exc) {
            throw new IndexOutOfBoundsException("Index: "+index);
        }
    }

    /**
     * Replaces the element at the specified position in this list with the
     * specified element (optional operation).
     *
     * <p>This implementation first gets a list iterator pointing to the
     * indexed element (with <tt>listIterator(index)</tt>).  Then, it gets
     * the current element using <tt>ListIterator.next</tt> and replaces it
     * with <tt>ListIterator.set</tt>.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the list iterator does not
     * implement the <tt>set</tt> operation.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     * @throws IndexOutOfBoundsException     {@inheritDoc}
     */
    public E set(int index, E element) {
	try {
	    ListIterator<E> e = listIterator(index);
	    E oldVal = e.next();
	    e.set(element);
	    return oldVal;
	} catch (NoSuchElementException exc) {
	    throw new IndexOutOfBoundsException("Index: "+index);
	}
    }

    /**
     * Inserts the specified element at the specified position in this list
     * (optional operation).  Shifts the element currently at that position
     * (if any) and any subsequent elements to the right (adds one to their
     * indices).
     *
     * <p>This implementation first gets a list iterator pointing to the
     * indexed element (with <tt>listIterator(index)</tt>).  Then, it
     * inserts the specified element with <tt>ListIterator.add</tt>.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the list iterator does not
     * implement the <tt>add</tt> operation.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     * @throws IndexOutOfBoundsException     {@inheritDoc}
     */
    public void add(int index, E element) {
	try {
	    listIterator(index).add(element);
	} catch (NoSuchElementException exc) {
	    throw new IndexOutOfBoundsException("Index: "+index);
	}
    }

    /**
     * Removes the element at the specified position in this list (optional
     * operation).  Shifts any subsequent elements to the left (subtracts one
     * from their indices).  Returns the element that was removed from the
     * list.
     *
     * <p>This implementation first gets a list iterator pointing to the
     * indexed element (with <tt>listIterator(index)</tt>).  Then, it removes
     * the element with <tt>ListIterator.remove</tt>.
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the list iterator does not
     * implement the <tt>remove</tt> operation.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws IndexOutOfBoundsException     {@inheritDoc}
     */
    public E remove(int index) {
	try {
	    ListIterator<E> e = listIterator(index);
	    E outCast = e.next();
	    e.remove();
	    return outCast;
	} catch (NoSuchElementException exc) {
	    throw new IndexOutOfBoundsException("Index: "+index);
	}
    }


    // Bulk Operations

    /**
     * Inserts all of the elements in the specified collection into this
     * list at the specified position (optional operation).  Shifts the
     * element currently at that position (if any) and any subsequent
     * elements to the right (increases their indices).  The new elements
     * will appear in this list in the order that they are returned by the
     * specified collection's iterator.  The behavior of this operation is
     * undefined if the specified collection is modified while the
     * operation is in progress.  (Note that this will occur if the specified
     * collection is this list, and it's nonempty.)
     *
     * <p>This implementation gets an iterator over the specified collection and
     * a list iterator over this list pointing to the indexed element (with
     * <tt>listIterator(index)</tt>).  Then, it iterates over the specified
     * collection, inserting the elements obtained from the iterator into this
     * list, one at a time, using <tt>ListIterator.add</tt> followed by
     * <tt>ListIterator.next</tt> (to skip over the added element).
     *
     * <p>Note that this implementation will throw an
     * <tt>UnsupportedOperationException</tt> if the list iterator returned by
     * the <tt>listIterator</tt> method does not implement the <tt>add</tt>
     * operation.
     *
     * @throws UnsupportedOperationException {@inheritDoc}
     * @throws ClassCastException            {@inheritDoc}
     * @throws NullPointerException          {@inheritDoc}
     * @throws IllegalArgumentException      {@inheritDoc}
     * @throws IndexOutOfBoundsException     {@inheritDoc}
     */
    public boolean addAll(int index, Collection<? extends E> c) {
	try {
	    boolean modified = false;
	    ListIterator<E> e1 = listIterator(index);
	    Iterator<? extends E> e2 = c.iterator();
	    while (e2.hasNext()) {
		e1.add(e2.next());
		modified = true;
	    }
	    return modified;
	} catch (NoSuchElementException exc) {
	    throw new IndexOutOfBoundsException("Index: "+index);
	}
    }


    // Iterators

    /**
     * Returns an iterator over the elements in this list (in proper
     * sequence).<p>
     *
     * This implementation merely returns a list iterator over the list.
     *
     * @return an iterator over the elements in this list (in proper sequence)
     */
    public Iterator<E> iterator() {
        return listIterator();
    }

    /**
     * Returns a list iterator over the elements in this list (in proper
     * sequence).
     *
     * @param  index index of first element to be returned from the list
     *         iterator (by a call to the <code>next</code> method)
     * @return a list iterator over the elements in this list (in proper
     *         sequence)
     * @throws IndexOutOfBoundsException {@inheritDoc}
     */
    public abstract ListIterator<E> listIterator(int index);
}