Helper method that extracts the next token that must be a double as required by Double.parseDouble
and throws an Exception if there are no more tokens.
Returns a String formatter to limit the input length, the range of valid characters
and a regular expression (according to the java.util.regex packet) for input validation.
If the value provided by this method is not zero, the time
a cache entry resides in the cache before it is beeing evicted is
spread to a percentage around getMaxAgeMillis().