regular expression

Regular expressions

【 teacher 】 Yangzhou teaching director - Mr. Zeng 9:24:32
^[a-zA-Z0-9_-][email protected][a-zA-Z0-9_-]+(\.[a-zA-Z0-9_-]+)+$

【 teacher 】 Yangzhou teaching director - Mr. Zeng 9:24:49
^1(3[0-9]|5[0-3,5-9]|7[1-3,5-8]|8[0-9])\d{8}$

【 teacher 】 Yangzhou teaching director - Mr. Zeng 9:24:57
^[1-9]\d{5}(18|19|20|(3\d))\d{2}((0[1-9])|(1[0-2]))(([0-2][1-9])|10|20|30|31)\d{3}[0-9Xx]$

【 teacher 】 Yangzhou teaching director - Mr. Zeng 9:25:05
^.*(?=.{6,})(?=.*\d)(?=.*[A-Z])(?=.*[a-z])(?=.*[[email protected]#$%^&*? ]).*$

 

Rule string

password    ： Length not less than 8 position , Include case , Numbers , Special symbols

Phone number ：138  139  158  159  170  189…… after 8 Bit arbitrary

mailbox   ： [email protected]

Id card number    ：   xxxxxxYYYYMMDDxxxx

How to write regular

How is regular checked

Strings that conform to certain rules .

Common rules
        A: character
            x character x. give an example ：'a' According to the character a
            \\ Backslash character Express \.
            \n New line （ Line break ） operator ('\u000A') 
            \r A carriage return ('\u000D')

        B: Character class , Match symbol []
            [abc] a、b or c（ Simple class ） 
            [^abc] Any character , except a、b or c（ no ） 
            [a-zA-Z] a To z or A To Z, Both ends of the letter are included （ Range ） 
            [0-9] 0 To 9 The characters include

        C: Predefined character class
            . Any character . All I have is . Character itself , How to express it ? \.
            \d Numbers ：[0-9]
            \w Word characters ：[a-zA-Z_0-9]
                The things that make up words in regular expressions must have these things

"http://www.baidu.com"  ^[http]   [com]$
        D: Boundary matcher
            ^ The beginning of a row  
            $ End of line  
            \b Word boundaries  
                It's not where the words and characters are .
                give an example ：hello world?haha;xixi

In regular expressions , If the characters are given directly , It's the exact match . use \d Can match a number ,\w Can match a letter or number , therefore ：

• '00\d' Can match '007', But it doesn't match '00A';

• '\d\d\d' Can match '010';

• '\w\w' Can match 'js';

. Can match any character , therefore ：

• 'js.' Can match 'jsp'、'jss'、'js!' wait .

To match a longer character , In regular expressions , use * Represents any character （ Include 0 individual ）, use + Represents at least one character , use ? Express 0 Or 1 Characters , use {n} Express n Characters , use {n,m} Express n-m Characters ：

Let's take a complex example ：\d{3}\s+\d{3,8}.

Let's read it from left to right ：

1. \d{3} Represents a match 3 A digital , for example '010';

2. \s Can match a space （ Also include Tab Equal space character ）, therefore \s+ Indicates that there is at least one space , For example, match ' ','\t\t' etc. ;

3. \d{3,8} Express 3-8 A digital , for example '1234567'.

combined , The regular expression above can match the phone number with area code separated by any space .

If you want to match '010-12345' Such a number ？ because '-' Is a special character , In regular expressions , Use '\' escape , therefore , The rule above is \d{3}\-\d{3,8}.

Advanced

To make a more accurate match , It can be used [] Scope of representation , such as ：

• [0-9a-zA-Z\_] Can match a number 、 Letters or underscores ;

• [0-9a-zA-Z\_]+ Can be matched by at least one number 、 A string of letters or underscores , such as 'a100','0_Z','js2015' wait ;

• [a-zA-Z\_\$][0-9a-zA-Z\_\$]* Can be matched by letters or underscores 、$ start , Followed by any number by 、 Letters or underscores 、$ Composed string , That is to say JavaScript Allowed variable names ;

• [a-zA-Z\_\$][0-9a-zA-Z\_\$]{0, 19} A more precise limit on the length of a variable is 1-20 Characters （ front 1 Characters + The most behind 19 Characters ）.

A|B Can match A or B, therefore (J|j)ava(S|s)cript Can match 'JavaScript'、'Javascript'、'javaScript' perhaps 'javascript'.

^ Indicates the beginning of a line ,^\d Indicates that it must start with a number .

$ Indicates the end of the line ,\d$ Indicates that it must end with a number .

You may have noticed ,js It can also match 'jsp', But add ^js$ It becomes a whole line match , It can only match 'js' 了 .

        E:Greedy quantifiers  

            X? X, Not once or once
            X* X, Zero or more times
            X+ X, Once or more
            X{n} X, just n Time  
            X{n,} X, At least n Time  
            X{n,m} X, At least n Time , But no more than m Time

Write a test , Enter the mobile phone number to judge whether it meets the requirements .

public class RegexDemo {
    public static void main(String[] args) {
        // Input from keyboard 5-10 Digit number , Can't use 0 start
        Scanner scanner = new Scanner(System.in);
        System.out.println(" Please enter 5-10 Is the number ");
        String str = scanner.next();
        // Create regular objects
        String regex = "[1-9][0-9]{4,9}";
        boolean result = str.matches(regex);
        if (result){
            System.out.println(" The content you entered meets the requirements ");
        }else {
            System.out.println(" Unqualified ");
        }
    }
}

Write a test , Let the user enter a mobile number , Then judge whether the mobile phone number entered by the user conforms to the rules

public class RegexDemo {
    public static void main(String[] args) {
        // Input from keyboard 5-10 Digit number , Can't use 0 start
        Scanner scanner = new Scanner(System.in);
        System.out.println(" Please enter your mobile number ");
        String str = scanner.next();
        // Create regular objects
        String regex = "1[3-9]\\d{9}";
        boolean result = str.matches(regex);
        if (result){
            System.out.println(" The content you entered meets the requirements ");
        }else {
            System.out.println(" Unqualified ");
        }
    }
}

The regular expression of the mailbox matches

[email protected]
[email protected]
[email protected]
[email protected]

public class RegexDemo {
    public static void main(String[] args) {
        // Input from keyboard 5-10 Digit number , Can't use 0 start
        Scanner scanner = new Scanner(System.in);
        System.out.println(" Please enter email address ");
        String str = scanner.next();
        // Create regular objects
        String regex = "\\[email protected]\\w{2,8}(.\\w{2,3})+";
        boolean result = str.matches(regex);
        if (result){
            System.out.println(" The content you entered meets the requirements ");
        }else {
            System.out.println(" Unqualified ");
        }
    }
}