Review

class ToStringStyle {
    /**
     * <p>Append to the <code>toString</code> the detail of a
     * <code>double</code> array.</p>
     *
     * @param buffer  the <code>StringBuffer</code> to populate
     * @param fieldName  the field name, typically not used as already appended
     * @param array  the array to add to the <code>toString</code>,
     *  not <code>null</code>
     */
    protected void appendDetail(StringBuffer buffer, String fieldName, double[] array) {
        buffer.append(arrayStart);
        for (int i = 0; i < array.length; i++) {
            if (i > 0) {
                buffer.append(arraySeparator);
            }
            appendDetail(buffer, fieldName, array[i]);
        }
        buffer.append(arrayEnd);
    }

}