abstractlist.java

java源代码 请看看啊 提点宝贵的意见

     * 		  collection prevents it from being added to this List.
     * 
     * @throws IllegalArgumentException some aspect an element of the
     *		  specified collection prevents it from being added to this
     *		  List.
     * 
     * @throws IndexOutOfBoundsException index out of range (<tt>index &lt; 0
     *            || index &gt; size()</tt>).
     *
     * @throws NullPointerException if the specified collection is null.
     */
    public boolean addAll(int index, Collection c) {
	boolean modified = false;
	Iterator e = c.iterator();
	while (e.hasNext()) {
	    add(index++, e.next());
	    modified = true;
	}
	return modified;
    }


    // Iterators

    /**
     * Returns an iterator over the elements in this list in proper
     * sequence. <p>
     *
     * This implementation returns a straightforward implementation of the
     * iterator interface, relying on the backing list's <tt>size()</tt>,
     * <tt>get(int)</tt>, and <tt>remove(int)</tt> methods.<p>
     *
     * Note that the iterator returned by this method will throw an
     * <tt>UnsupportedOperationException</tt> in response to its
     * <tt>remove</tt> method unless the list's <tt>remove(int)</tt> method is
     * overridden.<p>
     *
     * This implementation can be made to throw runtime exceptions in the face
     * of concurrent modification, as described in the specification for the
     * (protected) <tt>modCount</tt> field.
     *
     * @return an iterator over the elements in this list in proper sequence.
     * 
     * @see #modCount
     */
    public Iterator iterator() {
	return new Itr();
    }

    /**
     * Returns an iterator of the elements in this list (in proper sequence).
     * This implementation returns <tt>listIterator(0)</tt>.
     * 
     * @return an iterator of the elements in this list (in proper sequence).
     * 
     * @see #listIterator(int)
     */
    public ListIterator listIterator() {
	return listIterator(0);
    }

    /**
     * Returns a list iterator of the elements in this list (in proper
     * sequence), starting at the specified position in the list.  The
     * specified index indicates the first element that would be returned by
     * an initial call to the <tt>next</tt> method.  An initial call to
     * the <tt>previous</tt> method would return the element with the
     * specified index minus one.<p>
     *
     * This implementation returns a straightforward implementation of the
     * <tt>ListIterator</tt> interface that extends the implementation of the
     * <tt>Iterator</tt> interface returned by the <tt>iterator()</tt> method.
     * The <tt>ListIterator</tt> implementation relies on the backing list's
     * <tt>get(int)</tt>, <tt>set(int, Object)</tt>, <tt>add(int, Object)</tt>
     * and <tt>remove(int)</tt> methods.<p>
     *
     * Note that the list iterator returned by this implementation will throw
     * an <tt>UnsupportedOperationException</tt> in response to its
     * <tt>remove</tt>, <tt>set</tt> and <tt>add</tt> methods unless the
     * list's <tt>remove(int)</tt>, <tt>set(int, Object)</tt>, and
     * <tt>add(int, Object)</tt> methods are overridden.<p>
     *
     * This implementation can be made to throw runtime exceptions in the
     * face of concurrent modification, as described in the specification for
     * the (protected) <tt>modCount</tt> field.
     *
     * @param index index of the first element to be returned from the list
     *		    iterator (by a call to the <tt>next</tt> method).
     * 
     * @return a list iterator of the elements in this list (in proper
     * 	       sequence), starting at the specified position in the list.
     * 
     * @throws IndexOutOfBoundsException if the specified index is out of
     *		  range (<tt>index &lt; 0 || index &gt; size()</tt>).
     * 
     * @see #modCount
     */
    public ListIterator listIterator(final int index) {
	if (index<0 || index>size())
	  throw new IndexOutOfBoundsException("Index: "+index);

	return new ListItr(index);
    }

    private class Itr implements Iterator {
	/**
	 * Index of element to be returned by subsequent call to next.
	 */
	int cursor = 0;

	/**
	 * Index of element returned by most recent call to next or
	 * previous.  Reset to -1 if this element is deleted by a call
	 * to remove.
	 */
	int lastRet = -1;

	/**
	 * The modCount value that the iterator believes that the backing
	 * List should have.  If this expectation is violated, the iterator
	 * has detected concurrent modification.
	 */
	int expectedModCount = modCount;

	public boolean hasNext() {
	    return cursor != size();
	}

	public Object next() {
            checkForComodification();
	    try {
		Object next = get(cursor);
		lastRet = cursor++;
		return next;
	    } catch(IndexOutOfBoundsException e) {
		checkForComodification();
		throw new NoSuchElementException();
	    }
	}

	public void remove() {
	    if (lastRet == -1)
		throw new IllegalStateException();
            checkForComodification();

	    try {
		AbstractList.this.remove(lastRet);
		if (lastRet < cursor)
		    cursor--;
		lastRet = -1;
		expectedModCount = modCount;
	    } catch(IndexOutOfBoundsException e) {
		throw new ConcurrentModificationException();
	    }
	}

	final void checkForComodification() {
	    if (modCount != expectedModCount)
		throw new ConcurrentModificationException();
	}
    }

    private class ListItr extends Itr implements ListIterator {
	ListItr(int index) {
	    cursor = index;
	}

	public boolean hasPrevious() {
	    return cursor != 0;
	}

        public Object previous() {
            checkForComodification();
            try {
                int i = cursor - 1;
                Object previous = get(i);
                lastRet = cursor = i;
                return previous;
            } catch(IndexOutOfBoundsException e) {
                checkForComodification();
                throw new NoSuchElementException();
            }
        }

	public int nextIndex() {
	    return cursor;
	}

	public int previousIndex() {
	    return cursor-1;
	}

	public void set(Object o) {
	    if (lastRet == -1)
		throw new IllegalStateException();
            checkForComodification();

	    try {
		AbstractList.this.set(lastRet, o);
		expectedModCount = modCount;
	    } catch(IndexOutOfBoundsException e) {
		throw new ConcurrentModificationException();
	    }
	}

	public void add(Object o) {
            checkForComodification();

	    try {
		AbstractList.this.add(cursor++, o);
		lastRet = -1;
		expectedModCount = modCount;
	    } catch(IndexOutOfBoundsException e) {
		throw new ConcurrentModificationException();
	    }
	}
    }

    /**
     * Returns a view of the portion of this list between <tt>fromIndex</tt>,
     * inclusive, and <tt>toIndex</tt>, exclusive.  (If <tt>fromIndex</tt> and
     * <tt>toIndex</tt> are equal, the returned list is empty.)  The returned
     * list is backed by this list, so changes in the returned list are
     * reflected in this list, and vice-versa.  The returned list supports all
     * of the optional list operations supported by this list.<p>
     *
     * This method eliminates the need for explicit range operations (of the
     * sort that commonly exist for arrays).  Any operation that expects a
     * list can be used as a range operation by operating on a subList view
     * instead of a whole list.  For example, the following idiom removes a
     * range of elements from a list:
     * <pre>
     *     list.subList(from, to).clear();
     * </pre>
     * Similar idioms may be constructed for <tt>indexOf</tt> and
     * <tt>lastIndexOf</tt>, and all of the algorithms in the
     * <tt>Collections</tt> class can be applied to a subList.<p>
     * 
     * The semantics of the list returned by this method become undefined if
     * the backing list (i.e., this list) is <i>structurally modified</i> in
     * any way other than via the returned list.  (Structural modifications are
     * those that change the size of the list, or otherwise perturb it in such
     * a fashion that iterations in progress may yield incorrect results.)<p>
     *
     * This implementation returns a list that subclasses
     * <tt>AbstractList</tt>.  The subclass stores, in private fields, the
     * offset of the subList within the backing list, the size of the subList
     * (which can change over its lifetime), and the expected
     * <tt>modCount</tt> value of the backing list.  There are two variants
     * of the subclass, one of which implements <tt>RandomAccess</tt>.
     * If this list implements <tt>RandomAccess</tt> the returned list will
     * be an instance of the subclass that implements <tt>RandomAccess</tt>.<p>
     *
     * The subclass's <tt>set(int, Object)</tt>, <tt>get(int)</tt>,
     * <tt>add(int, Object)</tt>, <tt>remove(int)</tt>, <tt>addAll(int,
     * Collection)</tt> and <tt>removeRange(int, int)</tt> methods all
     * delegate to the corresponding methods on the backing abstract list,
     * after bounds-checking the index and adjusting for the offset.  The
     * <tt>addAll(Collection c)</tt> method merely returns <tt>addAll(size,
     * c)</tt>.<p>
     *
     * The <tt>listIterator(int)</tt> method returns a "wrapper object" over a
     * list iterator on the backing list, which is created with the
     * corresponding method on the backing list.  The <tt>iterator</tt> method
     * merely returns <tt>listIterator()</tt>, and the <tt>size</tt> method
     * merely returns the subclass's <tt>size</tt> field.<p>
     *
     * All methods first check to see if the actual <tt>modCount</tt> of the
     * backing list is equal to its expected value, and throw a
     * <tt>ConcurrentModificationException</tt> if it is not.
     *
     * @param fromIndex low endpoint (inclusive) of the subList.
     * @param toIndex high endpoint (exclusive) of the subList.
     * @return a view of the specified range within this list.
     * @throws IndexOutOfBoundsException endpoint index value out of range
     *         <tt>(fromIndex &lt; 0 || toIndex &gt; size)</tt>
     * @throws IllegalArgumentException endpoint indices out of order
     * <tt>(fromIndex &gt; toIndex)</tt> */
    public List subList(int fromIndex, int toIndex) {
        return (this instanceof RandomAccess ?
                new RandomAccessSubList(this, fromIndex, toIndex) :
                new SubList(this, fromIndex, toIndex));
    }

    // Comparison and hashing

    /**
     * Compares the specified object with this list for equality.  Returns
     * <tt>true</tt> if and only if the specified object is also a list, both