Arrays.java

    /**
     * Copies the specified range of the specified array into a new array.
     * The initial index of the range ("from") must lie between zero
     * and "original.length", inclusive.  The value at
     * "original[from]" is placed into the initial element of the copy
     * (unless "from == original.length" or "from == to").
     * Values from subsequent elements in the original array are placed into
     * subsequent elements in the copy.  The final index of the range
     * ("to"), which must be greater than or equal to "from",
     * may be greater than "original.length", in which case
     * "null" is placed in all elements of the copy whose index is
     * greater than or equal to "original.length - from".  The length
     * of the returned array will be "to - from".
     *
     * Parameters:
     *      original:   the array from which a range is to be copied
     *      from:       the initial index of the range to be copied, inclusive
     *      to:         the final index of the range to be copied, exclusive.
     *                  (This index may lie outside the array.)
     *
     * Return value:
     *      a new array containing the specified range from the original array,
     *      truncated or padded with null characters to obtain the required length
     *
     * Exceptions thrown:
     *      ArrayIndexOutOfBoundsException  if "from < 0" or "from > original.length"
     *      IllegalArgumentException        if "from > to"
     *      NullPointerException            if "original" is null
     */
    public static char[] copyOfRange(char[] original, int from, int to) {
        int newLength = to - from;
        if (newLength < 0)
            throw new IllegalArgumentException(from + " > " + to);
        char[] copy = new char[newLength];
        System.arraycopy(original, from, copy, 0,
                         Math.min(original.length - from, newLength));
        return copy;
    }