Sample Analysis of regular Operation of JavaString Class

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First, apply regular expressions

1 code

Public class RegExp {public static void main (String [] args) throws Exception {if ("123" .numbers ("\\ d +")) {System.out.println ("made up of numbers!") ;} else {System.out.println ("not composed of numbers!") ;}

2 run

It's made up of numbers!

Two string substitution-filter the numbers in the string

1 code

Public class SubString {public static void main (String [] args) throws Exception {String str = "a1b22c333d4444e55555f6666666g"; String regex = "[0-9] +"; / / numbers appear one or more times / / String regex = "\\ d +"; / / numbers appear one or more times System.out.println (str.replaceAll (regex, "));}}

2 run

Abcdefg

Three regularities verify mailbox format

1 code

Import java.util.*;public class EmailValidation {public static void main (String [] args) throws Exception {String str = null; String regex = "\\ wicked @\ wicked.\\ w+"; Scanner reader = new Scanner (System.in); do {System.out.print ("Please enter a valid email address:"); str = reader.next (); System.out.println (str);} while (! str.matches (regex)); System.out.println ("email address is valid! Thank you for registering! ") ; reader.close ();}}

2 run

Please enter a valid email address: April to April. Please enter a valid email address: yy@qq.comyy@qq.com email address is valid! Thank you for registering!

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