Using Java to find substring of a bigger string using Regular Expression

Question

If I have a string like this   FOO BAR    I need a generic way to get the  BAR  string out of the string so that no matter what string is between the square brackets it would be able to get the string   e g   FOO DOG    DOG FOO CAT    CAT

User · Answer

FOO DOG   replaceAll                         This will return a string  taking only the string inside square brackets   This remove all string outside from square brackets   You can test this java sample code online  http   tpcg io wZoFu0  You can test this regex from here  https   regex101 com r oUAzsS 1

User · Answer

import java util    import java util regex Matcher  import java util regex Pattern   public static String get match String s  String p           returns first match of p in s for first group in regular expression      Matcher m   Pattern compile p  matcher s       return m find     m group 1           get match  FOO BAR                       returns  BAR   public static List lt String gt  get matches String s  String p           returns all matches of p in s for first group in regular expression      List lt String gt  matches   new ArrayList lt String gt         Matcher m   Pattern compile p  matcher s       while m find              matches add m group 1              return matches     get matches  FOO BAR  FOO CAT                       returns  BAR  CAT

User · Answer

This is a working example    RegexpExample java  package org regexp replace   import java util ArrayList  import java util List  import java util regex Matcher  import java util regex Pattern   public class RegexpExample       public static void main String   args                String string    var1 value1   var2 value2   var3 value3            Pattern pattern   Pattern compile                             Matcher matcher   pattern matcher string            List lt String gt  listMatches   new ArrayList lt String gt              while matcher find                          listMatches add matcher group 2                       for String s   listMatches                        System out println s                       It displays    value1 value2 value3

User · Answer

You should be able to use non-greedy quantifiers  specifically      You re going to probably want the following   Pattern MY PATTERN   Pattern compile                   This will give you a pattern that will match your string and put the text within the square brackets in the first group   Have a look at the Pattern API Documentation for more information   To extract the string  you could use something like the following   Matcher m   MY PATTERN matcher  FOO BAR     while  m find          String s   m group 1          s now contains  BAR

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I d define that I want a maximum number of non-  characters between   and    These need to be escaped with backslashes  and in Java  these need to be escaped again   and the definition of non-  is a character class  thus inside   and    i e           The result   FOO

User · Answer

Like this its work if you want to parse some string which is coming from mYearInDB toString     2013  it will give 2013  Matcher n   MY PATTERN matcher  FOO BAR   mYearInDB toString     while  n find       extracredYear    n group 1       s now contains  BAR            System out println  Extrated output is     extracredYear

User · Answer

assuming that no other closing square bracket is allowed within   FOO

User · Answer

String input    FOO BAR    String result   input substring input indexOf      1 input lastIndexOf          This will return the value between first     and last      Foo Bar     Bar  Foo Bar test      Bar test   Note  You should add error checking if the input string is not well formed

User · Answer

I think your regular expression would look like    FOO            Assuming that FOO going to be constant   So  to put this in Java   Pattern p   Pattern compile  FOO              Matcher m   p matcher inputLine

User · Answer

the non-regex way   String input    FOO BAR    extracted  extracted   input substring input indexOf      input indexOf          alternatively  for slightly better performance memory usage  thanks Hosam     String input    FOO BAR    extracted  extracted   input substring input indexOf      input lastIndexOf

User · Answer

This regexp works for me   form               example   form company details  0  name  form company details  0  common names  1  title    output   Match 1 1   company details Match 2 1   company details   Tested on http   rubular com

User · Answer

If you simply need to get whatever is between     the you can use              like this   Pattern regex   Pattern compile                     Matcher m   regex matcher str   if  m find          result   m group        If you need it to be of the form identifier       content     then you can limit extracting the content only when the identifier is a alphanumerical    a-zA-Z  a-z-A-Z0-9    s                This will validate things like Foo  Bar   or myDevice 123  input   for instance   Main issue  The main problem is when you want to extract the content of something like this   FOO BAR CAT 123   DOG FOO     The Regex won t work and will return BAR CAT 123 and FOO  If we change the Regex to          then we re OK but then  if you re trying to extract the content from more complex things like    FOO BAR CAT 123   DOG FOO     myOtherFoo BAR 5     None of the Regexes will work   The most accurate Regex to extract the proper content in all cases would be a lot more complex as it would need to balance    pairs and give you they content   A simpler solution  If your problems is getting complex and the content of the    arbitrary  you could instead balance the pairs of    and extract the string using plain old code rathe than a Regex   int i  int brackets   0  string c  result       for  i   input indexOf       i  lt  str length  i          c   str substring i  i   1       if  c                   brackets          else if  c                   brackets--          if  brackets  lt   0               break            result   result   c         This is more pseudo-code than real code  I m not a Java coder so I don t know if the syntax is correct  but it should be easy enough to improve upon  What count is that this code should work and allow you to extract the content of the     however complex it is

[java] Using Java to find substring of a bigger string using Regular Expression

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