What is the. * in a regular expression? Or. * +
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Brief introduction of regular expression
Regular expression, also known as regular expression. (English: Regular Expression, often abbreviated as regex, regexp or RE in code), a concept in computer science. Regular expressions are often used to retrieve and replace text that conforms to a certain pattern (rule).
Many programming languages support string manipulation using regular expressions. For example, a powerful regular expression engine is built into Perl. The concept of regular expressions was first popularized by tools in Unix, such as sed and grep. Regular expressions are usually abbreviated to "regex". The singular has regexp and regex, and the plural has regexps, regexes, and regexen.
This article focuses on. * in regular expressions. Or. * +, the details are as follows:
Recently to do a tool to extract the special content of text, always can not write regular expressions, often encounter. *? Or. * + these symbols, look them up online and finally know what they mean. Record the results of the online explanation:
One more in the back? Indicates lazy mode.
Must be used after * or +
Such as:
If regular matching is used for content non-lazy pattern matching in src
Src= ". *"
The matching result is: src= "test.jpg" width= "60px" height= "80px"
It means from = "match back to the end of the match."
Laziness pattern is regular:
Src= ". *?"
Result: src= test.jpg
Because the match ends once when it reaches the first match. It won't continue to match backwards. Because he's lazy.
. Represents any character except\ n
* indicates match 0-infinity
+ means match 1-infinity
Remove the parenthesis instance
Public class Test {public static void main (String [] args) {String s = "img=32,34) http://www.sds.com/jpg(/img) picture (img=32,34) http://www.sds.com/jpg(/img)"; System.out.println (s.replaceAll ("\\ [. +?\] ","));}}
Results:
Picture http://www.sds.com/jpg Picture http://www.sds.com/jpg
Summary
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