What are the Pattern and Matcher classes in java and how do they differ?
My second question is, can you explain the following validation code clearly?
Pattern p = Pattern.compile("^[a-zA-Z][a-zA-Z\\s]+$");
Pattern pattern = Pattern.compile("\\d{10}");
Matcher--> A Matcher is created from a Pattern by invoking the Pattern's matcher method. The Matcher will match the given pattern (used to create it) against the String to be matched.
Pattern--> A compiled representation of a regular expression. A regular expression, specified as a string, must first be compiled into an instance of this class.
Pattern p = Pattern.compile("^[a-zA-Z][a-zA-Z\\s]+$");
// creates a regex pattern that can match a character followed by one or more characters or space
example : `ab` or `asa[space]` but not `a2` or `a` or `2`
Pattern pattern = Pattern.compile("\\d{10}");
// creates a regex pattern which can match exactly 10 digits
example : 1234567890