Basic knowledge about regular expressions

1. ". "is a wildcard that represents any character, for example,". c can match "anc", "abc", and "acc". 2. "[]". You can specify the matching characters in []. For example: "a [nbc] c" can match "anc", "abc", and "acc", but it cannot match "ancc". a to z can be written as [a-z], 0 to 9 can be written as [0-9]; 3. quantity limit symbol, indicating the number of matches (or length): including: "*" -- 0 or multiple times "+" -- 1 or multiple times "?" -- 0 times or 1 time "{n}" -- match n times, n is an integer "{n, m}" -- the number of times a number from n to m is matched; both n and m are integers; "{n ,}" -- match any number of times between n and infinity;" {, m} "-- match any number of times between 0 and m; they are placed behind the matching format: for example, the phone number: 024-84820482,02484820482 (assume that the first 3 or 4 digits, the last 7 or 8 digits, and the minus signs in the middle are optional, the following format can be used for matching: [0-9] {3, 4 }\\-? [0-9] {}; note: "\" is an escape character, because "-" represents a range in a regular expression, for example: as mentioned above [0-9], it must escape the character "\" for conversion. 4. "^" indicates no, indicating that it does not want to match, for example, [^ z] [a-z] + can match all character strings except those starting with "z" (length greater than 2, because "+" indicates the number of times greater than or equal to 1, and is a lowercase English character from the second digit); If ^ is placed outside [], it indicates a string starting; ^ [az] [a-z] + indicates an English character string starting with a or z with a length greater than or equal to 2; 5, "|", or operator, for example: a [n | bc | cb] c can match "abcc", "anc", and "acbc". 6. "$" ends with the character before it. For example: AB + $ can be matched by "abb" and "AB". 7. Some Simple Representation Methods: \ d indicates [0-9]. \ D represents [^ 0-9]; \ w represents [A-Z0-9]; \ W represents [^ A-Z0-9]; \ s represents [\ T \ n \ r \ f], that is, the space characters include tab, space, and so on; \ S indicates [^ \ t \ n \ r \ f], which is a non-space character. 8. Common matching: matching Chinese characters: "[\ u4e00-\ u9fa5]"; matching double-byte characters (including Chinese characters): "[^ \ x00-\ xff]"; regular Expression matching empty rows: \ n [\ s |] * \ r; Regular Expression matching HTML tags: "/. * |/"; Regular Expression matching the first and last spaces:" (^ \ s *) | (\ s * $) "; match non-negative integer (positive integer + 0 ): "^ \ d + $"; matches a positive integer: "^ [0-9] * [1-9] [0-9] * $ "; match a non-positive integer (negative integer + 0): "^ (-\ d +) | (0 +) $"; match a negative integer: "^-[0-9] * [1-9] [0-9] * $"; matching INTEGER: "^ -? \ D + $ "; match non-negative floating point number (Positive floating point number + 0):" ^ \ d + (\. \ d + )? $ "Matches Positive floating point:" ^ ([0-9] + \\. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * \. [0-9] +) | ([0-9] * [1-9] [0-9] *) $ "; ^ (-\ d + (\\. \ d + )?) | (0 + (\. 0 + )?)) $ // Match a non-Positive floating point number (negative floating point number + 0) ^ (-([0-9] + \\. [0-9] * [1-9] [0-9] *) | ([0-9] * [1-9] [0-9] * \. [0-9] +) | ([0-9] * [1-9] [0-9] *) $ // match the negative floating point number to match the Floating Point Number: "^ (-? \ D +) (\. \ d + )? $ "; Matches the string consisting of digits, 26 English letters, or underscores:" ^ \ w + $ "; matches the email address: "^ [\ w-] + (\\. [\ w-] +) * @ [\ w-] + (\\. [\ w-] +) + $ "; matched url:" ^ [a-zA-z] +: // match (\ w + (-\ w + )*)(\\. (\ w + (-\ w + )*))*(\\? \ S *)? $ "1,". "is a wildcard that represents any character, for example,". c can match "anc", "abc", and "acc". 2. "[]". You can specify the matching characters in []. For example: "a [nbc] c" can match "anc", "abc", and "acc", but it cannot match "ancc". a to z can be written as [a-z], 0 to 9 can be written as [0-9];...