Java Learning notes-Regular expressions

NO	Method name	Type	Describe
1	Public boolean matches (String regex)	Ordinary	Regular validation uses the
2	public string ReplaceAll (string regex,string replacement)	Ordinary	Replace All
3	public string Replacefirst (string regex,string replacement)	Ordinary	Replace the first
4	Public string[] Split (String regex)	Ordinary	Split all
5	Public string[] Split (String regex,int limit)	Ordinary	Partial split

Regular symbols (all regular match symbols are provided in Java.util.regex.Pattern;):

1. Represents a single character (each occurrence of one represents a bit):

• X: The representation is made up of X;
• \ \: Represents the transfer character "\"
• \ t: Indicates a tab, \ n = line break

2. Indicates the selection of characters (one for each occurrence):

• [ABC]: Indicates that it may be any of a B C (note: Only one character can be matched);

•  1  public  class   Demo1 { 2  3  public  static  void   Main (string[] args) { 4  //  TODO auto-generated method stub  5  String str= "a" ;  6  System.out.println (str.matches ("[ABC]" )); /span>7   " 8  9 } 

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•  Public class demo1 {    publicstaticvoid  main (string[] args) {        // TODO auto-generated Method stub        String str= "AB";        System.out.println (Str.matches ("[ABC][ABC]");}    }

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• [^ABC]: denotes any character except A, B, or C (negation)

• [A-za-z]:a to Z or A to Z, the letters at both ends are included (range)

• [0-9]:

3. Simplify the expression (one for each occurrence):

• .: denotes any one character;
• \d: Represents any one digit, equivalent to [0--9];

•      Public Static void Main (string[] args) {        //  TODO auto-generated method stub        String str= "2";        System.out.println (Str.matches ("\\d"));}    }

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• \d: Indicates not a number, equivalent to [^0--9];
• \s: denotes any one space;

•  Public class demo1 {    publicstaticvoid  main (string[] args) {        // TODO auto-generated Method stub        String str= "\ t";        System.out.println (Str.matches ("\\s"));}    }

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• \s: Represents a space that is not arbitrary;
• \w: denotes any digit in the alphanumeric underline of letters (including uppercase or lowercase);

4. Boundary Matching:

• ^: written before the regular, indicating the beginning of the regular;
• $: Written at the end of the regular, indicating a regular end;

5. Digital Specifications:

• ?: Indicates that the regular specification can only occur 0 or 1 times;

•  public  class   Demo1 { static  void   main (string[] args) {//  TODO auto-generated method stub  Strin        G str= "" ; System.out.println (Str.matches ( "\\d?")         = "
        
         ; System.out.println (Str1.matches (
         "\\d?")     

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• *: Indicates that there are 0 times 1 or more times;
• +: Indicates regular occurrences of 1 times & nbsp, or more than once;
• {n}: Indicates that this regular occurs exactly n times;
• {n}: Indicates that the regular appears n times and more than n times;
• {n,m}: Indicates that this regular appears n~m;

6. Logical expression:

• Regular x regular Y: Executes the regular x after the regular y;
• X| Y: One of the regular x or regular y can be satisfied;
• (regular): Indicates that more than one regular becomes a group;

7. Manipulating characters by using the String class:

• such as: Keep only letters

• 1  Public classDemo1 {2      Public Static voidMain (string[] args) {3         //TODO auto-generated Method Stub4String str= "AFAJHJ2313535{}]GAJ>? '; F ' Afag;lag ";5String regex= "[^a-za-z]";6System.out.println (Str.replaceall (Regex, ""));7     }8}

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• Replace (with the split () function)

•  Public class demo1 {    publicstaticvoid  main (string[] args) {        // TODO auto-generated Method stub        String str= "a1b22c333d4444e55555f666666g";        String regex= "\\d+";        String [] Res=str.split (regex);          for (int i=0;i<res.length;i++)            System.out.println (Res[i]);}    }

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• The user name is represented by an alphanumeric underscore and has 6~15 characters;

•  public  class   Demo1 { public  static  void   main (string[] args) { // 
       
         TODO auto-generated Method stub  String str= "wangxiang_123*" 
        ;        String regex  = "\\w{6,15}" 
        ;        System.out.println (Str.matches (regex)); String regex1  = "(\\d|[        a-za-z]|_|\\*) {6,15} "
        ;    System.out.println (Str.matches (REGEX1)); }}  
       

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• Now the students in a school record the "name: Age: Birthday: Results" format, such data can appear multiple times and separated by |, such as: allen:19:1993-05-02:98.6| judy:21:2000-09-02:78| sara:20:1994-08-21:97.5
• The following is a split of the individual judgments:
  • Name:

  • String str= "Zhansan"; String regex= "[a-za-z]+";

  • Age:

  • String str= "n"; String regex= "\\d{1,3}";

  • Birthday:

  • String str= "1993-09-02"; String regex= "\\d{4}-\\d{2}-\\d{2}";

  • Results:

  • String str= "98.98"; String regex= "\\d{1,3} (\\.\\d{1,2})?";

  • Single Student format synthesis:

  • String str= "allen:19:1993-05-02:98.6"; String regex= "[a-za-z]+:\\d{1,3}:\\d{4}-\\d{2}-\\d{2}:\\d{1,3} (\\.\\d{1,2})?";

  • The whole judgment:

  •  Public class demo1 {    publicstaticvoid  main (string[] args) {        // TODO auto-generated Method stub        String str= "allen:19:1993-05-02:98.6| judy:21:2000-09-02:78| sara:20:1994-08-21:97.5 ";        String Regex= "([a-za-z]+:\\d{1,3}:\\d{4}-\\d{2}-\\d{2}:\\d{1,3} (\\.\\d{1,2})?" \\|?) +";        System.out.println (Str.matches (regex));}    }

Java Learning notes-Regular expressions