Regular expression

• Regular expression uses a single string to describe it, which matches a series of search mode that conforms to a string that conforms to the rules of a sentence

• Use some mode to match the formula of a type of string

• Regular expression is similar to the contract in life. Use a special symbol to operate the string to determine whether the strings meet the rules of matching.

• Regular role:

  • Test the mode in the string
  • replace text
  • Extract the sub -string from the string

• advantage: great simplify code

• Disadvantages: Poor reading

 // Verify mobile phone number: 1. length 11 digits 2. Pure numbers 3. The second digit is [35789]
    private static void fun1() {
    
        String phone="13565248952";
        String reg="[1][35789][0-9]{9}";
        String reg1="1[35789]\\d{9}";
        boolean f = phone.matches(reg1);
        System.out.println(f);
    }

• Term Explanation: Cut the specified string according to the given rules (regular expression).

 // Cut
    private static void fun2() {
    
        String names="Zhang San. Li 4. Wang Ermazi";
        String[] ns = names.split("\\.");
        System.out.println(Arrays.toString(ns));
    }

• Term Explanation: Replace the specified string according to the given rules (regular expression) to a new string, the return value is string

// Replace-telephone
    private static void fun3() {
    
        String info="My doll has better experience, contact information: 13538384938";
        String newInfo = info.replaceAll("1[35789][0-9]{9}", "110");
        System.out.println(newInfo);
    }

• Filter stack words

 // Replace-stacking words-group
    private static void fun4() {
    
        String s="You are so fat, there are many meaty meat, you are good or bad!";
        // string reg = "(.) \\ 1 {1,}"; // 1: another time, twice
        String reg="(.)\\1+";// 1: Once again, twice in total
        String ss = s.replaceAll(reg, "$1");
        System.out.println(ss);

    }

• (.) Means matching any character, as a group
• (. (A)) The overall group is the first group\\1, inner layer (A) as the second group\\2
• $ 1 is used to remove the first group, $ 2 for the second group

// Replace-stacking words-group
    private static void fun5() {
    
        // Differential matching and obtaining
        String s="Eat";
        String reg="(. (Rice) {2})" "";
        // string reg = "(. (Rice)) \\ 2";
        String ss = s.replaceAll(reg, "$1");
        System.out.println(ss);// Eat for meals

        String s1="Eat and meals";
        String reg2="(. (Rice) {2}) \\ 1";
        String h = s1.replaceAll(reg2, "$1");
        System.out.println(h);// Eat meals
    }

// 1: Bai Bing: I like you
    private static void fun6() {
    
        String s="Bai Bing: I like to happy ... happy ... happy .. Huan ... Huanhuan .. Huanhuan. Huan .... You";
        // 1. Replace. ""
        String reg="\\.+";
        String s1 = s.replaceAll(reg, "");
        System.out.println(s1);
        // 2. Remove words-grouping I like to love you
        String reg2="(.)\\1+";
        String s2 = s1.replaceAll(reg2, "$1");
        System.out.println(s2);
    }

• mailbox verification

/* 
     Mail 
     Module 1: Numbers, letters, lower line length 3-12 
     Module 2: Either pure numbers or pure letters, length 2-6 
     Module three: .com.cn appeared 1-3 times 
      */

    private static void fun7() {
    
        String mail="[email protected]";
        String reg="\\w{3,12}@(\\d{2,6}|[a-zA-Z]{2,6})(\\.[a-z]{2,3}){1,2}";
        boolean f = mail.matches(reg);
        System.out.println(f);

    }

• Age

// Age 130 1-99 | 100-129 | 130
    private static void fun8() {
    
        String age="-13";
        String reg="[1-9]\\d?|1[012]\\d|130";
        System.out.println(age.matches(reg));

    }

• Chinese characters and spaces

 private static void fun9() {
    
       String s="Hello";
       String reg="^[\\u4e00-\\u9fa5]{2}\\s{2}";
        boolean m = s.matches(reg);
        System.out.println(m);

    }

<form id="form1" action="http://111.13.100.91/" method="post">
    <table border="1" width="600">
        <tr>
            <td>Nickname:</td>
            <td><input type="text" name="nick" pattern=".{4,10}" required placeholder="Please enter 4-10 characters"></td>
        </tr>
        <tr>
            <td>Password:</td>
            <td><input type="password" name="pwd" pattern=".{6,16}" required placeholder="Please enter 6-16-bit characters"></td>
        </tr>
        <tr>
            <td>mobile number:</td>
            <td><input type="text" name="phone" pattern="1[35789]\d{9}" required placeholder="Please enter the correct mobile phone number"></td>
        </tr>
        <tr>
            <td>mailbox:</td>
            <td><input type="email" name="email" required placeholder="Please enter the correct mailbox format"></td>
        </tr>
        <tr>
            <td>Age:</td>
            <td><input type="text" pattern="^[1-9]\d*$" name="age" placeholder="Please enter a positive number"></td>
        </tr>
        <tr>
            <td><input type="submit" value="Registration"></td>
            <td><input type="reset" value="reset"></td>
        </tr>
    </table>
</form>