How to check if a String contains another String in a case insensitive manner in Java

Question

Say I have two strings   String s1    AbBaCca   String s2    bac     I want to perform a check returning that s2 is contained within s1  I can do this with   return s1 contains s2     I am pretty sure that contains   is case sensitive  however I can t determine this for sure from reading the documentation  If it is then I suppose my best method would be something like   return s1 toLowerCase   contains s2 toLowerCase       All this aside  is there another  possibly better  way to accomplish this without caring about case-sensitivity

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import java text Normalizer   import org apache commons lang3 StringUtils   public class ContainsIgnoreCase        public static void main String   args             String in       Annul  e            String key    annulee               100  java         if  Normalizer normalize in  Normalizer Form NFD  replaceAll     p InCombiningDiacriticalMarks         toLowerCase   contains key                 System out println  OK              else               System out println  KO                          use commons lang lib         if  StringUtils containsIgnoreCase Normalizer normalize in  Normalizer Form NFD  replaceAll     p InCombiningDiacriticalMarks          key                 System out println  OK              else               System out println  KO

User · Answer

A simpler way of doing this  without worrying about pattern matching  would be converting both Strings to lowercase   String foobar    fooBar   String bar    FOO   if  foobar toLowerCase   contains bar toLowerCase          System out println  It s a match

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You can use regular expressions  and it works   boolean found   s1 matches    i       s2

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String container     Case SeNsitive    String sub    sen   if  rcontains container  sub         System out println  no case       public static Boolean rcontains String container  String sub         Boolean b   false      for  int a   0  a  lt  container length   - sub length     1  a                System out println sub     to     container substring a  a sub length              if  sub equalsIgnoreCase container substring a  a   sub length                    b   true                      return b      Basically  it is a method that takes two strings  It is supposed to be a not-case sensitive version of contains    When using the contains method  you want to see if one string is contained in the other   This method takes the string that is  sub  and checks if it is equal to the substrings of the container string that are equal in length to the  sub   If you look at the for loop  you will see that it iterates in substrings  that are the length of the  sub   over the container string   Each iteration checks to see if the substring of the container string is equalsIgnoreCase to the sub

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Yes  this is achievable   String s1    abBaCca   String s2    bac    String s1Lower   s1     s1Lower is exact same string  now convert it to lowercase  I left the s1 intact for print purposes if needed  s1Lower   s1Lower toLowerCase     String trueStatement    FALSE    if  s1Lower contains s2            THIS statement will be TRUE     trueStatement    TRUE      return trueStatement    This code will return the String  TRUE   as it found that your characters were contained

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Yes  contains is case sensitive   You can use java util regex Pattern with the CASE INSENSITIVE flag for case insensitive matching   Pattern compile Pattern quote wantedStr   Pattern CASE INSENSITIVE  matcher source  find      EDIT  If s2 contains regex special characters  of which there are many  it s important to quote it first   I ve corrected my answer since it is the first one people will see  but vote up Matt Quail s since he pointed this out

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We can use stream with anyMatch and contains of Java 8  public class Test2       public static void main String   args             String a    Gina Gini Protijayi Soudipta           String b    Gini            System out println WordPresentOrNot a  b            main      private static boolean WordPresentOrNot String a  String b          contains is case sensitive  That s why change it to upper or lower case  Then check            Here we are using stream with anyMatch         boolean match   Arrays stream a toLowerCase   split       anyMatch b toLowerCase    contains           return match

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You could simply do something like this   String s1    AbBaCca   String s2    bac   String toLower   s1 toLowerCase    return toLower contains s2

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One problem with the answer by Dave L  is when s2 contains regex markup such as  d  etc   You want to call Pattern quote   on s2   Pattern compile Pattern quote s2   Pattern CASE INSENSITIVE  matcher s1  find

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A simpler way of doing this  without worrying about pattern matching  would be converting both Strings to lowercase   String foobar    fooBar   String bar    FOO   if  foobar toLowerCase   contains bar toLowerCase          System out println  It s a match

User · Answer

A Faster Implementation  Utilizing String regionMatches    Using regexp can be relatively slow  It  being slow  doesn t matter if you just want to check in one case  But if you have an array or a collection of thousands or hundreds of thousands of strings  things can get pretty slow   The presented solution below doesn t use regular expressions nor toLowerCase    which is also slow because it creates another strings and just throws them away after the check    The solution builds on the String regionMatches   method which seems to be unknown  It checks if 2 String regions match  but what s important is that it also has an overload with a handy ignoreCase parameter   public static boolean containsIgnoreCase String src  String what        final int length   what length        if  length    0          return true     Empty string is contained      final char firstLo   Character toLowerCase what charAt 0        final char firstUp   Character toUpperCase what charAt 0         for  int i   src length   - length  i  gt   0  i--               Quick check before calling the more expensive regionMatches   method          final char ch   src charAt i           if  ch    firstLo  amp  amp  ch    firstUp              continue           if  src regionMatches true  i  what  0  length               return true             return false      Speed Analysis  This speed analysis does not mean to be rocket science  just a rough picture of how fast the different methods are   I compare 5 methods    Our containsIgnoreCase   method  By converting both strings to lower-case and call String contains    By converting source string to lower-case and call String contains   with the pre-cached  lower-cased substring  This solution is already not as flexible because it tests a predefiend substring  Using regular expression  the accepted answer Pattern compile   matcher   find       Using regular expression but with pre-created and cached Pattern  This solution is already not as flexible because it tests a predefined substring    Results  by calling the method 10 million times     Our method  670 ms 2x toLowerCase   and contains    2829 ms 1x toLowerCase   and contains   with cached substring  2446 ms Regexp  7180 ms Regexp with cached Pattern  1845 ms   Results in a table                                               RELATIVE SPEED   1 RELATIVE SPEED  METHOD                          EXEC TIME    TO SLOWEST      TO FASTEST   1  ------------------------------------------------------------------------------  1  Using regionMatches            670 ms       10 7x            1 0x  2  2x lowercase contains         2829 ms        2 5x            4 2x  3  1x lowercase contains cache   2446 ms        2 9x            3 7x  4  Regexp                        7180 ms        1 0x           10 7x  5  Regexp cached pattern         1845 ms        3 9x            2 8x   Our method is 4x faster compared to lowercasing and using contains    10x faster compared to using regular expressions and also 3x faster even if the Pattern is pre-cached  and losing flexibility of checking for an arbitrary substring      Analysis Test Code  If you re interested how the analysis was performed  here is the complete runnable application   import java util regex Pattern   public class ContainsAnalysis           Case 1 utilizing String regionMatches       public static boolean containsIgnoreCase String src  String what            final int length   what length            if  length    0              return true     Empty string is contained          final char firstLo   Character toLowerCase what charAt 0            final char firstUp   Character toUpperCase what charAt 0             for  int i   src length   - length  i  gt   0  i--                   Quick check before calling the more expensive regionMatches                  method              final char ch   src charAt i               if  ch    firstLo  amp  amp  ch    firstUp                  continue               if  src regionMatches true  i  what  0  length                   return true                     return false                Case 2 with 2x toLowerCase   and contains       public static boolean containsConverting String src  String what            return src toLowerCase   contains what toLowerCase                   The cached substring for case 3     private static final String S    i am  toLowerCase            Case 3 with pre-cached substring and 1x toLowerCase   and contains       public static boolean containsConverting String src            return src toLowerCase   contains S                 Case 4 with regexp     public static boolean containsIgnoreCaseRegexp String src  String what            return Pattern compile Pattern quote what   Pattern CASE INSENSITIVE                       matcher src  find                  The cached pattern for case 5     private static final Pattern P   Pattern compile              Pattern quote  i am    Pattern CASE INSENSITIVE           Case 5 with pre-cached Pattern     public static boolean containsIgnoreCaseRegexp String src            return P matcher src  find                  Main method  perfroms speed analysis on different contains methods         case ignored      public static void main String   args  throws Exception           final String src    Hi  I am Adam           final String what    i am            long start  end          final int N   10 000 000           start   System nanoTime            for  int i   0  i  lt  N  i                containsIgnoreCase src  what           end   System nanoTime            System out println  Case 1 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsConverting src  what           end   System nanoTime            System out println  Case 2 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsConverting src           end   System nanoTime            System out println  Case 3 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsIgnoreCaseRegexp src  what           end   System nanoTime            System out println  Case 4 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsIgnoreCaseRegexp src           end   System nanoTime            System out println  Case 5 took       end - start    1000000     ms

User · Answer

I did a test finding a case-insensitive match of a string  I have a Vector of 150 000 objects all with a String as one field and wanted to find the subset which matched a string  I tried three methods    Convert all to lower case  for  SongInformation song  songs        if  song artist toLowerCase   indexOf pattern toLowercase    gt  -1                             Use the String matches   method  for  SongInformation song  songs        if  song artist matches    i       pattern                             Use regular expressions  Pattern p   Pattern compile pattern  Pattern CASE INSENSITIVE   Matcher m   p matcher      for  SongInformation song  songs        m reset song artist       if  m find                         Timing results are    No attempted match  20 msecs To lower match  182 msecs String matches  278 msecs Regular expression  65 msecs   The regular expression looks to be the fastest for this use case

User · Answer

Yes  contains is case sensitive   You can use java util regex Pattern with the CASE INSENSITIVE flag for case insensitive matching   Pattern compile Pattern quote wantedStr   Pattern CASE INSENSITIVE  matcher source  find      EDIT  If s2 contains regex special characters  of which there are many  it s important to quote it first   I ve corrected my answer since it is the first one people will see  but vote up Matt Quail s since he pointed this out

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Yes  this is achievable   String s1    abBaCca   String s2    bac    String s1Lower   s1     s1Lower is exact same string  now convert it to lowercase  I left the s1 intact for print purposes if needed  s1Lower   s1Lower toLowerCase     String trueStatement    FALSE    if  s1Lower contains s2            THIS statement will be TRUE     trueStatement    TRUE      return trueStatement    This code will return the String  TRUE   as it found that your characters were contained

User · Answer

There is a simple concise way  using regex flag  case insensitive  i      String s1    hello abc efg    String s2    ABC    s1 matches      i   s2                   denotes every character except line break      i  denotes case insensitivity flag enabled for s2  String

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Here s some Unicode-friendly ones you can make if you pull in ICU4j  I guess  ignore case  is questionable for the method names because although primary strength comparisons do ignore case  it s described as the specifics being locale-dependent  But it s hopefully locale-dependent in a way the user would expect   public static boolean containsIgnoreCase String haystack  String needle        return indexOfIgnoreCase haystack  needle   gt   0     public static int indexOfIgnoreCase String haystack  String needle        StringSearch stringSearch   new StringSearch needle  haystack       stringSearch getCollator   setStrength Collator PRIMARY       return stringSearch first

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I m not sure what your main question is here  but yes   contains is case sensitive

User · Answer

I m not sure what your main question is here  but yes   contains is case sensitive

User · Answer

You could simply do something like this   String s1    AbBaCca   String s2    bac   String toLower   s1 toLowerCase    return toLower contains s2

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If you have to search an ASCII string in another ASCII string  such as a URL  you will find my solution to be better  I ve tested icza s method and mine for the speed and here are the results    Case 1 took 2788 ms - regionMatches Case 2 took 1520 ms - my   The code   public static String lowerCaseAscii String s        if  s    null          return null       int len   s length        char   buf   new char len       s getChars 0  len  buf  0       for  int i 0  i lt len  i              if  buf i   gt    A   amp  amp  buf i   lt    Z               buf i     0x20             return new String buf      public static boolean containsIgnoreCaseAscii String str  String searchStr        return StringUtils contains lowerCaseAscii str   lowerCaseAscii searchStr

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You can use   org apache commons lang3 StringUtils containsIgnoreCase  AbBaCca    bac      The Apache Commons library is very useful for this sort of thing  And this particular one may be better than regular expressions as regex is always expensive in terms of performance

User · Answer

We can use stream with anyMatch and contains of Java 8  public class Test2       public static void main String   args             String a    Gina Gini Protijayi Soudipta           String b    Gini            System out println WordPresentOrNot a  b            main      private static boolean WordPresentOrNot String a  String b          contains is case sensitive  That s why change it to upper or lower case  Then check            Here we are using stream with anyMatch         boolean match   Arrays stream a toLowerCase   split       anyMatch b toLowerCase    contains           return match

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AbCd  toLowerCase   contains  abcD  toLowerCase

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One problem with the answer by Dave L  is when s2 contains regex markup such as  d  etc   You want to call Pattern quote   on s2   Pattern compile Pattern quote s2   Pattern CASE INSENSITIVE  matcher s1  find

User · Answer

I m not sure what your main question is here  but yes   contains is case sensitive

User · Answer

Yes  contains is case sensitive   You can use java util regex Pattern with the CASE INSENSITIVE flag for case insensitive matching   Pattern compile Pattern quote wantedStr   Pattern CASE INSENSITIVE  matcher source  find      EDIT  If s2 contains regex special characters  of which there are many  it s important to quote it first   I ve corrected my answer since it is the first one people will see  but vote up Matt Quail s since he pointed this out

User · Answer

import java text Normalizer   import org apache commons lang3 StringUtils   public class ContainsIgnoreCase        public static void main String   args             String in       Annul  e            String key    annulee               100  java         if  Normalizer normalize in  Normalizer Form NFD  replaceAll     p InCombiningDiacriticalMarks         toLowerCase   contains key                 System out println  OK              else               System out println  KO                          use commons lang lib         if  StringUtils containsIgnoreCase Normalizer normalize in  Normalizer Form NFD  replaceAll     p InCombiningDiacriticalMarks          key                 System out println  OK              else               System out println  KO

User · Answer

You can use   org apache commons lang3 StringUtils containsIgnoreCase  AbBaCca    bac      The Apache Commons library is very useful for this sort of thing  And this particular one may be better than regular expressions as regex is always expensive in terms of performance

User · Answer

AbCd  toLowerCase   contains  abcD  toLowerCase

User · Answer

Yes  contains is case sensitive   You can use java util regex Pattern with the CASE INSENSITIVE flag for case insensitive matching   Pattern compile Pattern quote wantedStr   Pattern CASE INSENSITIVE  matcher source  find      EDIT  If s2 contains regex special characters  of which there are many  it s important to quote it first   I ve corrected my answer since it is the first one people will see  but vote up Matt Quail s since he pointed this out

User · Answer

String container     Case SeNsitive    String sub    sen   if  rcontains container  sub         System out println  no case       public static Boolean rcontains String container  String sub         Boolean b   false      for  int a   0  a  lt  container length   - sub length     1  a                System out println sub     to     container substring a  a sub length              if  sub equalsIgnoreCase container substring a  a   sub length                    b   true                      return b      Basically  it is a method that takes two strings  It is supposed to be a not-case sensitive version of contains    When using the contains method  you want to see if one string is contained in the other   This method takes the string that is  sub  and checks if it is equal to the substrings of the container string that are equal in length to the  sub   If you look at the for loop  you will see that it iterates in substrings  that are the length of the  sub   over the container string   Each iteration checks to see if the substring of the container string is equalsIgnoreCase to the sub

User · Answer

or you can use a simple approach and just convert the string s case to substring s case and then use contains method

User · Answer

If you have to search an ASCII string in another ASCII string  such as a URL  you will find my solution to be better  I ve tested icza s method and mine for the speed and here are the results    Case 1 took 2788 ms - regionMatches Case 2 took 1520 ms - my   The code   public static String lowerCaseAscii String s        if  s    null          return null       int len   s length        char   buf   new char len       s getChars 0  len  buf  0       for  int i 0  i lt len  i              if  buf i   gt    A   amp  amp  buf i   lt    Z               buf i     0x20             return new String buf      public static boolean containsIgnoreCaseAscii String str  String searchStr        return StringUtils contains lowerCaseAscii str   lowerCaseAscii searchStr

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Here s some Unicode-friendly ones you can make if you pull in ICU4j  I guess  ignore case  is questionable for the method names because although primary strength comparisons do ignore case  it s described as the specifics being locale-dependent  But it s hopefully locale-dependent in a way the user would expect   public static boolean containsIgnoreCase String haystack  String needle        return indexOfIgnoreCase haystack  needle   gt   0     public static int indexOfIgnoreCase String haystack  String needle        StringSearch stringSearch   new StringSearch needle  haystack       stringSearch getCollator   setStrength Collator PRIMARY       return stringSearch first

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String x  abCd   System out println Pattern compile  c  Pattern CASE INSENSITIVE  matcher x  find

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I m not sure what your main question is here  but yes   contains is case sensitive

User · Answer

You can use regular expressions  and it works   boolean found   s1 matches    i       s2

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String x  abCd   System out println Pattern compile  c  Pattern CASE INSENSITIVE  matcher x  find

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or you can use a simple approach and just convert the string s case to substring s case and then use contains method

User · Answer

A Faster Implementation  Utilizing String regionMatches    Using regexp can be relatively slow  It  being slow  doesn t matter if you just want to check in one case  But if you have an array or a collection of thousands or hundreds of thousands of strings  things can get pretty slow   The presented solution below doesn t use regular expressions nor toLowerCase    which is also slow because it creates another strings and just throws them away after the check    The solution builds on the String regionMatches   method which seems to be unknown  It checks if 2 String regions match  but what s important is that it also has an overload with a handy ignoreCase parameter   public static boolean containsIgnoreCase String src  String what        final int length   what length        if  length    0          return true     Empty string is contained      final char firstLo   Character toLowerCase what charAt 0        final char firstUp   Character toUpperCase what charAt 0         for  int i   src length   - length  i  gt   0  i--               Quick check before calling the more expensive regionMatches   method          final char ch   src charAt i           if  ch    firstLo  amp  amp  ch    firstUp              continue           if  src regionMatches true  i  what  0  length               return true             return false      Speed Analysis  This speed analysis does not mean to be rocket science  just a rough picture of how fast the different methods are   I compare 5 methods    Our containsIgnoreCase   method  By converting both strings to lower-case and call String contains    By converting source string to lower-case and call String contains   with the pre-cached  lower-cased substring  This solution is already not as flexible because it tests a predefiend substring  Using regular expression  the accepted answer Pattern compile   matcher   find       Using regular expression but with pre-created and cached Pattern  This solution is already not as flexible because it tests a predefined substring    Results  by calling the method 10 million times     Our method  670 ms 2x toLowerCase   and contains    2829 ms 1x toLowerCase   and contains   with cached substring  2446 ms Regexp  7180 ms Regexp with cached Pattern  1845 ms   Results in a table                                               RELATIVE SPEED   1 RELATIVE SPEED  METHOD                          EXEC TIME    TO SLOWEST      TO FASTEST   1  ------------------------------------------------------------------------------  1  Using regionMatches            670 ms       10 7x            1 0x  2  2x lowercase contains         2829 ms        2 5x            4 2x  3  1x lowercase contains cache   2446 ms        2 9x            3 7x  4  Regexp                        7180 ms        1 0x           10 7x  5  Regexp cached pattern         1845 ms        3 9x            2 8x   Our method is 4x faster compared to lowercasing and using contains    10x faster compared to using regular expressions and also 3x faster even if the Pattern is pre-cached  and losing flexibility of checking for an arbitrary substring      Analysis Test Code  If you re interested how the analysis was performed  here is the complete runnable application   import java util regex Pattern   public class ContainsAnalysis           Case 1 utilizing String regionMatches       public static boolean containsIgnoreCase String src  String what            final int length   what length            if  length    0              return true     Empty string is contained          final char firstLo   Character toLowerCase what charAt 0            final char firstUp   Character toUpperCase what charAt 0             for  int i   src length   - length  i  gt   0  i--                   Quick check before calling the more expensive regionMatches                  method              final char ch   src charAt i               if  ch    firstLo  amp  amp  ch    firstUp                  continue               if  src regionMatches true  i  what  0  length                   return true                     return false                Case 2 with 2x toLowerCase   and contains       public static boolean containsConverting String src  String what            return src toLowerCase   contains what toLowerCase                   The cached substring for case 3     private static final String S    i am  toLowerCase            Case 3 with pre-cached substring and 1x toLowerCase   and contains       public static boolean containsConverting String src            return src toLowerCase   contains S                 Case 4 with regexp     public static boolean containsIgnoreCaseRegexp String src  String what            return Pattern compile Pattern quote what   Pattern CASE INSENSITIVE                       matcher src  find                  The cached pattern for case 5     private static final Pattern P   Pattern compile              Pattern quote  i am    Pattern CASE INSENSITIVE           Case 5 with pre-cached Pattern     public static boolean containsIgnoreCaseRegexp String src            return P matcher src  find                  Main method  perfroms speed analysis on different contains methods         case ignored      public static void main String   args  throws Exception           final String src    Hi  I am Adam           final String what    i am            long start  end          final int N   10 000 000           start   System nanoTime            for  int i   0  i  lt  N  i                containsIgnoreCase src  what           end   System nanoTime            System out println  Case 1 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsConverting src  what           end   System nanoTime            System out println  Case 2 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsConverting src           end   System nanoTime            System out println  Case 3 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsIgnoreCaseRegexp src  what           end   System nanoTime            System out println  Case 4 took       end - start    1000000     ms             start   System nanoTime            for  int i   0  i  lt  N  i                containsIgnoreCaseRegexp src           end   System nanoTime            System out println  Case 5 took       end - start    1000000     ms

User · Answer

One problem with the answer by Dave L  is when s2 contains regex markup such as  d  etc   You want to call Pattern quote   on s2   Pattern compile Pattern quote s2   Pattern CASE INSENSITIVE  matcher s1  find

User · Answer

I did a test finding a case-insensitive match of a string  I have a Vector of 150 000 objects all with a String as one field and wanted to find the subset which matched a string  I tried three methods    Convert all to lower case  for  SongInformation song  songs        if  song artist toLowerCase   indexOf pattern toLowercase    gt  -1                             Use the String matches   method  for  SongInformation song  songs        if  song artist matches    i       pattern                             Use regular expressions  Pattern p   Pattern compile pattern  Pattern CASE INSENSITIVE   Matcher m   p matcher      for  SongInformation song  songs        m reset song artist       if  m find                         Timing results are    No attempted match  20 msecs To lower match  182 msecs String matches  278 msecs Regular expression  65 msecs   The regular expression looks to be the fastest for this use case

User · Answer

There is a simple concise way  using regex flag  case insensitive  i      String s1    hello abc efg    String s2    ABC    s1 matches      i   s2                   denotes every character except line break      i  denotes case insensitivity flag enabled for s2  String

User · Answer

One problem with the answer by Dave L  is when s2 contains regex markup such as  d  etc   You want to call Pattern quote   on s2   Pattern compile Pattern quote s2   Pattern CASE INSENSITIVE  matcher s1  find

[java] How to check if a String contains another String in a case insensitive manner in Java?

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