vector.java

java源代码 请看看啊 提点宝贵的意见

     * @since 1.2
     */
    public synchronized Object[] toArray(Object a[]) {
        if (a.length < elementCount)
            a = (Object[])java.lang.reflect.Array.newInstance(
                                a.getClass().getComponentType(), elementCount);

	System.arraycopy(elementData, 0, a, 0, elementCount);

        if (a.length > elementCount)
            a[elementCount] = null;

        return a;
    }

    // Positional Access Operations

    /**
     * Returns the element at the specified position in this Vector.
     *
     * @param index index of element to return.
     * @return object at the specified index
     * @exception ArrayIndexOutOfBoundsException index is out of range (index
     * 		  &lt; 0 || index &gt;= size()).
     * @since 1.2
     */
    public synchronized Object get(int index) {
	if (index >= elementCount)
	    throw new ArrayIndexOutOfBoundsException(index);

	return elementData[index];
    }

    /**
     * Replaces the element at the specified position in this Vector with the
     * specified element.
     *
     * @param index index of element to replace.
     * @param element element to be stored at the specified position.
     * @return the element previously at the specified position.
     * @exception ArrayIndexOutOfBoundsException index out of range
     *		  (index &lt; 0 || index &gt;= size()).
     * @since 1.2
     */
    public synchronized Object set(int index, Object element) {
	if (index >= elementCount)
	    throw new ArrayIndexOutOfBoundsException(index);

	Object oldValue = elementData[index];
	elementData[index] = element;
	return oldValue;
    }

    /**
     * Appends the specified element to the end of this Vector.
     *
     * @param o element to be appended to this Vector.
     * @return true (as per the general contract of Collection.add).
     * @since 1.2
     */
    public synchronized boolean add(Object o) {
	modCount++;
	ensureCapacityHelper(elementCount + 1);
	elementData[elementCount++] = o;
        return true;
    }

    /**
     * Removes the first occurrence of the specified element in this Vector
     * If the Vector does not contain the element, it is unchanged.  More
     * formally, removes the element with the lowest index i such that
     * <code>(o==null ? get(i)==null : o.equals(get(i)))</code> (if such
     * an element exists).
     *
     * @param o element to be removed from this Vector, if present.
     * @return true if the Vector contained the specified element.
     * @since 1.2
     */
    public boolean remove(Object o) {
        return removeElement(o);
    }

    /**
     * Inserts the specified element at the specified position in this Vector.
     * Shifts the element currently at that position (if any) and any
     * subsequent elements to the right (adds one to their indices).
     *
     * @param index index at which the specified element is to be inserted.
     * @param element element to be inserted.
     * @exception ArrayIndexOutOfBoundsException index is out of range
     *		  (index &lt; 0 || index &gt; size()).
     * @since 1.2
     */
    public void add(int index, Object element) {
        insertElementAt(element, index);
    }

    /**
     * Removes the element at the specified position in this Vector.
     * shifts any subsequent elements to the left (subtracts one from their
     * indices).  Returns the element that was removed from the Vector.
     *
     * @exception ArrayIndexOutOfBoundsException index out of range (index
     * 		  &lt; 0 || index &gt;= size()).
     * @param index the index of the element to removed.
     * @return element that was removed
     * @since 1.2
     */
    public synchronized Object remove(int index) {
	modCount++;
	if (index >= elementCount)
	    throw new ArrayIndexOutOfBoundsException(index);
	Object oldValue = elementData[index];

	int numMoved = elementCount - index - 1;
	if (numMoved > 0)
	    System.arraycopy(elementData, index+1, elementData, index,
			     numMoved);
	elementData[--elementCount] = null; // Let gc do its work

	return oldValue;
    }

    /**
     * Removes all of the elements from this Vector.  The Vector will
     * be empty after this call returns (unless it throws an exception).
     *
     * @since 1.2
     */
    public void clear() {
        removeAllElements();
    }

    // Bulk Operations

    /**
     * Returns true if this Vector contains all of the elements in the
     * specified Collection.
     *
     * @param   c a collection whose elements will be tested for containment
     *          in this Vector
     * @return true if this Vector contains all of the elements in the
     *	       specified collection.
     * @throws NullPointerException if the specified collection is null.
     */
    public synchronized boolean containsAll(Collection c) {
        return super.containsAll(c);
    }

    /**
     * Appends all of the elements in the specified Collection to the end of
     * this Vector, 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.
     * (This implies that the behavior of this call is undefined if the
     * specified Collection is this Vector, and this Vector is nonempty.)
     *
     * @param c elements to be inserted into this Vector.
     * @return <tt>true</tt> if this Vector changed as a result of the call.
     * @throws NullPointerException if the specified collection is null.
     * @since 1.2
     */
    public synchronized boolean addAll(Collection c) {
	modCount++;
        Object[] a = c.toArray();
        int numNew = a.length;
	ensureCapacityHelper(elementCount + numNew);
        System.arraycopy(a, 0, elementData, elementCount, numNew);
        elementCount += numNew;
	return numNew != 0;
    }

    /**
     * Removes from this Vector all of its elements that are contained in the
     * specified Collection.
     *
     * @param c a collection of elements to be removed from the Vector
     * @return true if this Vector changed as a result of the call.
     * @throws NullPointerException if the specified collection is null.
     * @since 1.2
     */
    public synchronized boolean removeAll(Collection c) {
        return super.removeAll(c);
    }

    /**
     * Retains only the elements in this Vector that are contained in the
     * specified Collection.  In other words, removes from this Vector all
     * of its elements that are not contained in the specified Collection. 
     *
     * @param c a collection of elements to be retained in this Vector
     *          (all other elements are removed)
     * @return true if this Vector changed as a result of the call.
     * @throws NullPointerException if the specified collection is null.
     * @since 1.2
     */
    public synchronized boolean retainAll(Collection c)  {
        return super.retainAll(c);
    }

    /**
     * Inserts all of the elements in in the specified Collection into this
     * Vector at the specified position.  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 the Vector  
     * in the order that they are returned by the specified Collection's
     * iterator.
     *
     * @param index index at which to insert first element
     *		    from the specified collection.
     * @param c elements to be inserted into this Vector.
     * @return <tt>true</tt> if this Vector changed as a result of the call.
     * @exception ArrayIndexOutOfBoundsException index out of range (index
     *		  &lt; 0 || index &gt; size()).
     * @throws NullPointerException if the specified collection is null.
     * @since 1.2
     */
    public synchronized boolean addAll(int index, Collection c) {
	modCount++;
	if (index < 0 || index > elementCount)
	    throw new ArrayIndexOutOfBoundsException(index);

        Object[] a = c.toArray();
	int numNew = a.length;
	ensureCapacityHelper(elementCount + numNew);

	int numMoved = elementCount - index;
	if (numMoved > 0)
	    System.arraycopy(elementData, index, elementData, index + numNew,
			     numMoved);

        System.arraycopy(a, 0, elementData, index, numNew);
	elementCount += numNew;
	return numNew != 0;
    }

    /**
     * Compares the specified Object with this Vector for equality.  Returns
     * true if and only if the specified Object is also a List, both Lists
     * have the same size, and all corresponding pairs of elements in the two
     * Lists are <em>equal</em>.  (Two elements <code>e1</code> and
     * <code>e2</code> are <em>equal</em> if <code>(e1==null ? e2==null :
     * e1.equals(e2))</code>.)  In other words, two Lists are defined to be
     * equal if they contain the same elements in the same order.
     *
     * @param o the Object to be compared for equality with this Vector.
     * @return true if the specified Object is equal to this Vector
     */
    public synchronized boolean equals(Object o) {
        return super.equals(o);
    }

    /**
     * Returns the hash code value for this Vector.
     */
    public synchronized int hashCode() {
        return super.hashCode();
    }

    /**
     * Returns a string representation of this Vector, containing
     * the String representation of each element.
     */
    public synchronized String toString() {
        return super.toString();
    }

    /**
     * Returns a view of the portion of this List between fromIndex,
     * inclusive, and toIndex, exclusive.  (If fromIndex and ToIndex 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 indexOf and lastIndexOf,
     * and all of the algorithms in the Collections 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.)
     *
     * @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
     *         <code>(fromIndex &lt; 0 || toIndex &gt; size)</code>
     * @throws IllegalArgumentException endpoint indices out of order
     *	       <code>(fromIndex &gt; toIndex)</code>
     */
    public synchronized List subList(int fromIndex, int toIndex) {
        return Collections.synchronizedList(super.subList(fromIndex, toIndex),
                                            this);
    }

    /**
     * Removes from this List all of the elements whose index is between
     * fromIndex, inclusive and toIndex, exclusive.  Shifts any succeeding
     * elements to the left (reduces their index).
     * This call shortens the ArrayList by (toIndex - fromIndex) elements.  (If
     * toIndex==fromIndex, this operation has no effect.)
     *
     * @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) {
	modCount++;
	int numMoved = elementCount - toIndex;
        System.arraycopy(elementData, toIndex, elementData, fromIndex,
                         numMoved);

	// Let gc do its work
	int newElementCount = elementCount - (toIndex-fromIndex);
	while (elementCount != newElementCount)
	    elementData[--elementCount] = null;
    }

    /**
     * Save the state of the <tt>Vector</tt> instance to a stream (that
     * is, serialize it).  This method is present merely for synchronization.
     * It just calls the default readObject method.
     */
    private synchronized void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException
    {
	s.defaultWriteObject();
    }
}