Create array of regex matches

Question

In Java  I am trying to return all regex matches to an array but it seems that you can only check whether the pattern matches something or not  boolean    How can I use a regex match to form an array of all string matching a regex expression in a given string

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Here s a simple example   Pattern pattern   Pattern compile regexPattern   List lt String gt  list   new ArrayList lt String gt     Matcher m   pattern matcher input   while  m find          list add m group          if you have more capturing groups  you can refer to them by their index as an argument of the group method  If you need an array  then use list toArray

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Set lt String gt  keyList   new HashSet            Pattern regex   Pattern compile                          Matcher matcher   regex matcher  Content goes here            while matcher find                  keyList add matcher group 1                       return keyList

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In Java 9  you can now use Matcher results   to get a Stream lt MatchResult gt  which you can use to get a list array of matches   import java util regex Pattern  import java util regex MatchResult      String   matches   Pattern compile  your regex here                              matcher  string to search from here                              results                              map MatchResult  group                             toArray String    new                          or  collect Collectors toList

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From the Official Regex Java Trails           Pattern pattern            Pattern compile console readLine   nEnter your regex                Matcher matcher            pattern matcher console readLine  Enter input string to search                boolean found   false          while  matcher find                  console format  I found the text    s   starting at                     index  d and ending at index  d  n                   matcher group    matcher start    matcher end                 found   true              Use find and insert the resulting group at your array   List   whatever

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4castle s answer is better than the below if you can assume Java    9   You need to create a matcher and use that to iteratively find matches    import java util regex Matcher   import java util regex Pattern          List lt String gt  allMatches   new ArrayList lt String gt      Matcher m   Pattern compile  your regular expression here         matcher yourStringHere    while  m find         allMatches add m group          After this  allMatches contains the matches  and you can use allMatches toArray new String 0   to get an array if you really need one     You can also use MatchResult to write helper functions to loop over matches since Matcher toMatchResult   returns a snapshot of the current group state   For example you can write a lazy iterator to let you do  for  MatchResult match   allMatches pattern  input          Use match  and maybe break without doing the work to find all possible matches      by doing something like this   public static Iterable lt MatchResult gt  allMatches        final Pattern p  final CharSequence input      return new Iterable lt MatchResult gt          public Iterator lt MatchResult gt  iterator           return new Iterator lt MatchResult gt                 Use a matcher internally          final Matcher matcher   p matcher input              Keep a match around that supports any interleaving of hasNext next calls          MatchResult pending           public boolean hasNext                  Lazily fill pending  and avoid calling find   multiple times if the              clients call hasNext   repeatedly before sampling via next              if  pending    null  amp  amp  matcher find                  pending   matcher toMatchResult                          return pending    null                     public MatchResult next                  Fill pending if necessary  as when clients call next   without              checking hasNext     throw if not possible            if   hasNext      throw new NoSuchElementException                   Consume pending so next call to hasNext   does a find              MatchResult next   pending            pending   null            return next                         Required to satisfy the interface  but unsupported             public void remove     throw new UnsupportedOperationException                              With this   for  MatchResult match   allMatches Pattern compile   abc      abracadabra        System out println match group       at     match start         yields   a at 0 b at 1 a at 3 c at 4 a at 5 a at 7 b at 8 a at 10

User · Answer

Java makes regex too complicated and it does not follow the perl-style  Take a look at MentaRegex to see how you can accomplish that in a single line of Java code   String   matches   match  aa11bb22        d   g          gt    11    22

[java] Create array of regex matches

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