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This article shows you an overview and simple use, the content is concise and easy to understand, can definitely brighten your eyes, through the detailed introduction of this article, I hope you can get something.

Overview and simple use of regular expressions

* A: regular expression

* is a single string used to describe or match a series of strings that conform to certain grammatical rules. It's actually a rule. Has its own special application.

* function: for example, a registered mailbox has a user name and password, and its length is generally limited. This limit is done by regular expressions.

* B: case demonstration

* demand: check the qq number.

* 1: must be 5-15 digits

* cannot start at 2:0

* 3: it must all be numeric

* a: non-regular expression implementation

* b: regular expression implementation

Case study:

Package com.heima.regex

Public class Demo1_Regex {

Public static void main (String [] args) {

System.out.println (checkQQ ("012345"))

System.out.println (checkQQ ("a1b345"))

System.out.println (checkQQ ("123456"))

System.out.println (checkQQ ("1234567890987654321"))

String regex = "[1-9]\\ d {4pm 14}"

System.out.println ("2553868" .vendor (regex))

System.out.println ("012345" .vendor (regex))

System.out.println ("2553868abc" .vendor (regex))

}

/ *

* demand: check the qq number.

* 1: must be 5-15 digits

* cannot start at 2:0

* 3: it must all be numeric

* verify qq

* 1. Specify the return value type boolean

* 2, clear parameter list String qq

, /

Public static boolean checkQQ (String qq) {

Boolean flag = true; / / set flag to false if the verification qq does not meet the requirements, and return directly if it meets the requirements

If (qq.length ()) > = 5 & & qq.length () ='0' & & ch

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