[Java] Regular Expression:Pattern,Mather,Scanner

1. Docs
2. Important Classes
   
   • Pattern
     Patterns are compiled regular expressions. If you need to do a lot of work with the same regular expression, it may be more efficient to compile it once and reuse it.
     
   • Matcher
     The result of applying a Pattern to a given input.
     
   • StringTokenizer
     Break a string into tokens according to delimiters.
   • Scanner
     Parses a text string of primitive types and strings. It supports localized numbers and various radixes.
   • String.matches, String.replaceAll, String.split
     In many cases, convenience methods such as String.matches, String.replaceAll and String.split will be preferable.
     
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