Most memory efficient way to grow an array in Java?

Question

I\'m not too concerned about time efficiency (the operation will be rare), but rather about memory efficiency: Can I grow the array without temporarily having all th

Answer 1

AFAIK the only way of growing or reducing an array is doing a System.arraycopy

   /**
    * 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 (index
    *     < 0 || index >= length).
    */
    public static  T[] removeArrayIndex(T[] src, int index) {
        Object[] tmp = src.clone();

        int size = tmp.length;
        if ((index < 0) && (index >= size)) {
            throw new ArrayIndexOutOfBoundsException(index);
        }

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

        return (T[]) Arrays.copyOf(tmp, size - 1);
    }

   /**
    * Inserts the element at the specified position in this list.
    * Shifts any subsequent elements to the rigth (adds one to their indices).
    *
    * @param index the index of the element to inserted.
    * @return the element that is inserted in the list.
    * @throws    IndexOutOfBoundsException if index out of range (index
    *     < 0 || index >= length).
    */
    public static  T[] insertArrayIndex(T[] src, Object newData, int index) {
        Object[] tmp = null;
        if (src == null) {
            tmp = new Object[index+1];
        } else {
            tmp = new Object[src.length+1];

            int size = tmp.length;
            if ((index < 0) && (index >= size)) {
                throw new ArrayIndexOutOfBoundsException(index);
            }

            System.arraycopy(src, 0, tmp, 0, index);
            System.arraycopy(src, index, tmp, index+1, src.length-index);
        }

        tmp[index] = newData;

        return (T[]) Arrays.copyOf(tmp, tmp.length);
    }