public static OptionalDouble parseDouble(String value) {
        if (value == null) {
            return OptionalDouble.empty();
        } else {
            return OptionalDouble.of(Double.parseDouble(value));
        }
    }
Parses the specified value into an optional unless it is {@code null}, 
in which case an empty optional is returned.

@param value  the value (or null)
@return       the wrapped optional
runtime-parent/runtime-core/src/main/java/com/speedment/runtime/core/util/OptionalUtil.java