public static <T> ToDoubleOrElse<T>
    doubleOrElse(ToDoubleNullable<T> expression, double defaultValue) {
        return new ToDoubleOrElseImpl<>(expression, defaultValue);
    }
Returns an expression that returns the same value as the specified
expression if it is not {@code null}, and if the wrapped expression
returns {@code null}, then the default value is returned instead.

@param expression    the nullable expression to wrap
@param defaultValue  the default value to use
@param <T>           the input entity type
@return              the non-nullable expression
runtime-parent/runtime-compute/src/main/java/com/speedment/runtime/compute/internal/expression/OrElseUtil.java