arraylist.java

来自「This is a resource based on j2me embedde」· Java 代码 · 共 584 行 · 第 1/2 页

    /**
     * Returns an array containing all of the elements in this list
     * in the correct order.
     *
     * @return an array containing all of the elements in this list
     * 	       in the correct order.
     */
    public Object[] toArray() {
	Object[] result = new Object[size];
	System.arraycopy(elementData, 0, result, 0, size);
	return result;
    }

    /**
     * Returns an array containing all of the elements in this list in the
     * correct order; the runtime type of the returned array is that of the
     * specified array.  If the list fits in the specified array, it is
     * returned therein.  Otherwise, a new array is allocated with the runtime
     * type of the specified array and the size of this list.<p>
     *
     * If the list fits in the specified array with room to spare (i.e., the
     * array has more elements than the list), the element in the array
     * immediately following the end of the collection is set to
     * <tt>null</tt>.  This is useful in determining the length of the list
     * <i>only</i> if the caller knows that the list does not contain any
     * <tt>null</tt> elements.
     *
     * @param a the array into which the elements of the list are to
     *		be stored, if it is big enough; otherwise, a new array of the
     * 		same runtime type is allocated for this purpose.
     * @return an array containing the elements of the list.
     * @throws ArrayStoreException if the runtime type of a is not a supertype
     *         of the runtime type of every element in this list.
     */
    public Object[] toArray(Object a[]) {
        if (a.length < size)
            a = (Object[])java.lang.reflect.Array.newInstance(
                                a.getClass().getComponentType(), size);

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

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

        return a;
    }

    // Positional Access Operations

    /**
     * Returns the element at the specified position in this list.
     *
     * @param  index index of element to return.
     * @return the element at the specified position in this list.
     * @throws    IndexOutOfBoundsException if index is out of range <tt>(index
     * 		  &lt; 0 || index &gt;= size())</tt>.
     */
    public Object get(int index) {
	RangeCheck(index);

	return elementData[index];
    }

    /**
     * Replaces the element at the specified position in this list 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.
     * @throws    IndexOutOfBoundsException if index out of range
     *		  <tt>(index &lt; 0 || index &gt;= size())</tt>.
     */
    public Object set(int index, Object element) {
	RangeCheck(index);

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

    /**
     * Appends the specified element to the end of this list.
     *
     * @param o element to be appended to this list.
     * @return <tt>true</tt> (as per the general contract of Collection.add).
     */
    public boolean add(Object o) {
	ensureCapacity(size + 1);  // Increments modCount!!
	elementData[size++] = o;
	return true;
    }

    /**
     * Inserts the specified element at the specified position in this
     * list. 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.
     * @throws    IndexOutOfBoundsException if index is out of range
     *		  <tt>(index &lt; 0 || index &gt; size())</tt>.
     */
    public void add(int index, Object element) {
	if (index > size || index < 0)
	    throw new IndexOutOfBoundsException(
		"Index: "+index+", Size: "+size);

	ensureCapacity(size+1);  // Increments modCount!!
/* IAI - 15 */
	CVM.copyObjectArray(elementData, index, elementData, index + 1,
			 size - index);
/* IAI - 15 */
	elementData[index] = element;
	size++;
    }

    /**
     * Removes the element at the specified position in this list.
     * Shifts any subsequent elements to the left (subtracts one from their
     * indices).
     *
     * @param index the index of the element to removed.
     * @return the element that was removed from the list.
     * @throws    IndexOutOfBoundsException if index out of range <tt>(index
     * 		  &lt; 0 || index &gt;= size())</tt>.
     */
    public Object remove(int index) {
	RangeCheck(index);

	modCount++;
	Object oldValue = elementData[index];

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

	return oldValue;
    }

    /**
     * Removes all of the elements from this list.  The list will
     * be empty after this call returns.
     */
    public void clear() {
	modCount++;

	// Let gc do its work
	for (int i = 0; i < size; i++)
	    elementData[i] = null;

	size = 0;
    }

    /**
     * Appends all of the elements in the specified Collection to the end of
     * 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.  (This implies that the behavior of this call is
     * undefined if the specified Collection is this list, and this
     * list is nonempty.)
     *
     * @param c the elements to be inserted into this list.
     * @return <tt>true</tt> if this list changed as a result of the call.
     * @throws    NullPointerException if the specified collection is null.
     */
    public boolean addAll(Collection c) {
        Object[] a = c.toArray();
        int numNew = a.length;
	ensureCapacity(size + numNew);  // Increments modCount
/* IAI - 15 */
        CVM.copyObjectArray(a, 0, elementData, size, numNew);
/* IAI - 15 */
        size += numNew;
	return numNew != 0;
    }

    /**
     * Inserts all of the elements in the specified Collection into this
     * list, starting 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 list 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 list.
     * @return <tt>true</tt> if this list changed as a result of the call.
     * @throws    IndexOutOfBoundsException if 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) {
	if (index > size || index < 0)
	    throw new IndexOutOfBoundsException(
		"Index: " + index + ", Size: " + size);

        Object[] a = c.toArray();
	int numNew = a.length;
	ensureCapacity(size + numNew);  // Increments modCount

	int numMoved = size - index;
	if (numMoved > 0) {
/* IAI - 15 */
	    CVM.copyObjectArray(elementData, index, elementData, index + numNew,
			     numMoved);
        }

        CVM.copyObjectArray(a, 0, elementData, index, numNew);
/* IAI - 15 */
	size += numNew;
	return numNew != 0;
    }

    /**
     * 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 list by <tt>(toIndex - fromIndex)</tt> elements.
     * (If <tt>toIndex==fromIndex</tt>, 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 = size - toIndex;
        System.arraycopy(elementData, toIndex, elementData, fromIndex,
                         numMoved);

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

    /**
     * Check if the given index is in range.  If not, throw an appropriate
     * runtime exception.  This method does *not* check if the index is
     * negative: It is always used immediately prior to an array access,
     * which throws an ArrayIndexOutOfBoundsException if index is negative.
     */
    private void RangeCheck(int index) {
	if (index >= size)
	    throw new IndexOutOfBoundsException(
		"Index: "+index+", Size: "+size);
    }

    /**
     * Save the state of the <tt>ArrayList</tt> instance to a stream (that
     * is, serialize it).
     *
     * @serialData The length of the array backing the <tt>ArrayList</tt>
     *             instance is emitted (int), followed by all of its elements
     *             (each an <tt>Object</tt>) in the proper order.
     */
    private void writeObject(java.io.ObjectOutputStream s)
        throws java.io.IOException{
	// Write out element count, and any hidden stuff
	s.defaultWriteObject();

        // Write out array length
        s.writeInt(elementData.length);

	// Write out all elements in the proper order.
	for (int i=0; i<size; i++)
            s.writeObject(elementData[i]);
    }

    /**
     * Reconstitute the <tt>ArrayList</tt> instance from a stream (that is,
     * deserialize it).
     */
    private void readObject(java.io.ObjectInputStream s)
        throws java.io.IOException, ClassNotFoundException {
	// Read in size, and any hidden stuff
	s.defaultReadObject();

        // Read in array length and allocate array
        int arrayLength = s.readInt();
        elementData = new Object[arrayLength];

	// Read in all elements in the proper order.
	for (int i=0; i<size; i++)
            elementData[i] = s.readObject();
    }
}