parse

Main.java

private static <T extends Number> Optional<T> parse(final String s, final Class<T> clazz)
    {
        // Escape if null input
        if ((s == null) || (clazz == null))
            return Optional.empty();


        Object parsed = null;
        NumberFormatException exception = null;

        try {
            // Integral types
            if (Byte.class.isAssignableFrom(clazz))
                parsed = Byte.parseByte(s);
            else if (Short.class.isAssignableFrom(clazz))
                parsed = Short.parseShort(s);
            else if (Integer.class.isAssignableFrom(clazz))
                parsed = Integer.parseInt(s);
            else if (Long.class.isAssignableFrom(clazz))
                parsed = Long.parseLong(s);

            // Floating point
            else if (Float.class.isAssignableFrom(clazz))
                parsed = Float.parseFloat(s);
            else if (Double.class.isAssignableFrom(clazz))
                parsed = Double.parseDouble(s);

            // Big numbers
            else if (BigInteger.class.isAssignableFrom(clazz))
                parsed = new BigInteger(s);
            else if (BigDecimal.class.isAssignableFrom(clazz))
                parsed = new BigDecimal(s);


            // Or else it will be null
        }
        catch (NumberFormatException e) {
            exception = e;
        }

        if (parsed != null)
        {
            if (clazz.isInstance(parsed))
            {
                @SuppressWarnings("unchecked")
                final T t = (T)parsed;

                return Optional.ofNullable(t);
            }
            else
            {
                System.err.println("Error: " + parsed.toString() + " must be a kind of " + clazz.getName());
            }
        }
        else if (exception != null)
        {
            System.err.println("Error: " + exception.getMessage() + ", unable to parse into " + clazz.getName());
        }
        else
        {
            System.err.println("Error: " + clazz.getName() + " extends Number, but cannot be processed");
        }

        return Optional.empty();
    }