abstractlist.java

java源代码 请看看啊 提点宝贵的意见

     * lists have the same size, and all corresponding pairs of elements in
     * the two lists are <i>equal</i>.  (Two elements <tt>e1</tt> and
     * <tt>e2</tt> are <i>equal</i> if <tt>(e1==null ? e2==null :
     * e1.equals(e2))</tt>.)  In other words, two lists are defined to be
     * equal if they contain the same elements in the same order.<p>
     *
     * This implementation first checks if the specified object is this
     * list. If so, it returns <tt>true</tt>; if not, it checks if the
     * specified object is a list. If not, it returns <tt>false</tt>; if so,
     * it iterates over both lists, comparing corresponding pairs of elements.
     * If any comparison returns <tt>false</tt>, this method returns
     * <tt>false</tt>.  If either iterator runs out of elements before the
     * other it returns <tt>false</tt> (as the lists are of unequal length);
     * otherwise it returns <tt>true</tt> when the iterations complete.
     *
     * @param o the object to be compared for equality with this list.
     * 
     * @return <tt>true</tt> if the specified object is equal to this list.
     */
    public boolean equals(Object o) {
	if (o == this)
	    return true;
	if (!(o instanceof List))
	    return false;

	ListIterator e1 = listIterator();
	ListIterator e2 = ((List) o).listIterator();
	while(e1.hasNext() && e2.hasNext()) {
	    Object o1 = e1.next();
	    Object o2 = e2.next();
	    if (!(o1==null ? o2==null : o1.equals(o2)))
		return false;
	}
	return !(e1.hasNext() || e2.hasNext());
    }

    /**
     * Returns the hash code value for this list. <p>
     *
     * This implementation uses exactly the code that is used to define the
     * list hash function in the documentation for the <tt>List.hashCode</tt>
     * method.
     *
     * @return the hash code value for this list.
     */
    public int hashCode() {
	int hashCode = 1;
	Iterator i = iterator();
     	while (i.hasNext()) {
	    Object obj = i.next();
	    hashCode = 31*hashCode + (obj==null ? 0 : obj.hashCode());
	}
	return hashCode;
    }

    /**
     * Removes from this list all of the elements whose index is between
     * <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive.
     * Shifts any succeeding elements to the left (reduces their index).  This
     * call shortens the ArrayList by <tt>(toIndex - fromIndex)</tt>
     * elements.  (If <tt>toIndex==fromIndex</tt>, this operation has no
     * effect.)<p>
     *
     * This method is called by the <tt>clear</tt> operation on this list
     * and its subLists.  Overriding this method to take advantage of
     * the internals of the list implementation can <i>substantially</i>
     * improve the performance of the <tt>clear</tt> operation on this list
     * and its subLists.<p>
     *
     * This implementation gets a list iterator positioned before
     * <tt>fromIndex</tt>, and repeatedly calls <tt>ListIterator.next</tt>
     * followed by <tt>ListIterator.remove</tt> until the entire range has
     * been removed.  <b>Note: if <tt>ListIterator.remove</tt> requires linear
     * time, this implementation requires quadratic time.</b>
     *
     * @param fromIndex index of first element to be removed.
     * @param toIndex index after last element to be removed.
     */
    protected void removeRange(int fromIndex, int toIndex) {
        ListIterator it = listIterator(fromIndex);
        for (int i=0, n=toIndex-fromIndex; i<n; i++) {
            it.next();
            it.remove();
        }
    }

    /**
     * The number of times this list has been <i>structurally modified</i>.
     * 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 field is used by the iterator and list iterator implementation
     * returned by the <tt>iterator</tt> and <tt>listIterator</tt> methods.
     * If the value of this field changes unexpectedly, the iterator (or list
     * iterator) will throw a <tt>ConcurrentModificationException</tt> in
     * response to the <tt>next</tt>, <tt>remove</tt>, <tt>previous</tt>,
     * <tt>set</tt> or <tt>add</tt> operations.  This provides
     * <i>fail-fast</i> behavior, rather than non-deterministic behavior in
     * the face of concurrent modification during iteration.<p>
     *
     * <b>Use of this field by subclasses is optional.</b> If a subclass
     * wishes to provide fail-fast iterators (and list iterators), then it
     * merely has to increment this field in its <tt>add(int, Object)</tt> and
     * <tt>remove(int)</tt> methods (and any other methods that it overrides
     * that result in structural modifications to the list).  A single call to
     * <tt>add(int, Object)</tt> or <tt>remove(int)</tt> must add no more than
     * one to this field, or the iterators (and list iterators) will throw
     * bogus <tt>ConcurrentModificationExceptions</tt>.  If an implementation
     * does not wish to provide fail-fast iterators, this field may be
     * ignored.
     */
    protected transient int modCount = 0;
}

class SubList extends AbstractList {
    private AbstractList l;
    private int offset;
    private int size;
    private int expectedModCount;

    SubList(AbstractList list, int fromIndex, int toIndex) {
        if (fromIndex < 0)
            throw new IndexOutOfBoundsException("fromIndex = " + fromIndex);
        if (toIndex > list.size())
            throw new IndexOutOfBoundsException("toIndex = " + toIndex);
        if (fromIndex > toIndex)
            throw new IllegalArgumentException("fromIndex(" + fromIndex +
                                               ") > toIndex(" + toIndex + ")");
        l = list;
        offset = fromIndex;
        size = toIndex - fromIndex;
        expectedModCount = l.modCount;
    }

    public Object set(int index, Object element) {
        rangeCheck(index);
        checkForComodification();
        return l.set(index+offset, element);
    }

    public Object get(int index) {
        rangeCheck(index);
        checkForComodification();
        return l.get(index+offset);
    }

    public int size() {
        checkForComodification();
        return size;
    }

    public void add(int index, Object element) {
        if (index<0 || index>size)
            throw new IndexOutOfBoundsException();
        checkForComodification();
        l.add(index+offset, element);
        expectedModCount = l.modCount;
        size++;
        modCount++;
    }

    public Object remove(int index) {
        rangeCheck(index);
        checkForComodification();
        Object result = l.remove(index+offset);
        expectedModCount = l.modCount;
        size--;
        modCount++;
        return result;
    }

    protected void removeRange(int fromIndex, int toIndex) {
        checkForComodification();
        l.removeRange(fromIndex+offset, toIndex+offset);
        expectedModCount = l.modCount;
        size -= (toIndex-fromIndex);
        modCount++;
    }

    public boolean addAll(Collection c) {
        return addAll(size, c);
    }

    public boolean addAll(int index, Collection c) {
        if (index<0 || index>size)
            throw new IndexOutOfBoundsException(
                "Index: "+index+", Size: "+size);
        int cSize = c.size();
        if (cSize==0)
            return false;

        checkForComodification();
        l.addAll(offset+index, c);
        expectedModCount = l.modCount;
        size += cSize;
        modCount++;
        return true;
    }

    public Iterator iterator() {
        return listIterator();
    }

    public ListIterator listIterator(final int index) {
        checkForComodification();
        if (index<0 || index>size)
            throw new IndexOutOfBoundsException(
                "Index: "+index+", Size: "+size);

        return new ListIterator() {
            private ListIterator i = l.listIterator(index+offset);

            public boolean hasNext() {
                return nextIndex() < size;
            }

            public Object next() {
                if (hasNext())
                    return i.next();
                else
                    throw new NoSuchElementException();
            }

            public boolean hasPrevious() {
                return previousIndex() >= 0;
            }

            public Object previous() {
                if (hasPrevious())
                    return i.previous();
                else
                    throw new NoSuchElementException();
            }

            public int nextIndex() {
                return i.nextIndex() - offset;
            }

            public int previousIndex() {
                return i.previousIndex() - offset;
            }

            public void remove() {
                i.remove();
                expectedModCount = l.modCount;
                size--;
                modCount++;
            }

            public void set(Object o) {
                i.set(o);
            }

            public void add(Object o) {
                i.add(o);
                expectedModCount = l.modCount;
                size++;
                modCount++;
            }
        };
    }

    public List subList(int fromIndex, int toIndex) {
        return new SubList(this, fromIndex, toIndex);
    }

    private void rangeCheck(int index) {
        if (index<0 || index>=size)
            throw new IndexOutOfBoundsException("Index: "+index+
                                                ",Size: "+size);
    }

    private void checkForComodification() {
        if (l.modCount != expectedModCount)
            throw new ConcurrentModificationException();
    }
}

class RandomAccessSubList extends SubList implements RandomAccess {
    RandomAccessSubList(AbstractList list, int fromIndex, int toIndex) {
        super(list, fromIndex, toIndex);
    }

    public List subList(int fromIndex, int toIndex) {
        return new RandomAccessSubList(this, fromIndex, toIndex);
    }
}