Replacing all non-alphanumeric characters with empty strings

Question

I tried using this but didn t work-  return value replaceAll     A-Za-z0-9

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Solution  value replaceAll  quot   A-Za-z0-9  quot    quot  quot   Explanation     abc  When a caret   appears as the first character inside square brackets  it negates the pattern  This pattern matches any character except a or b or c   Looking at the keyword as two function     Pattern     match Pattern     Pattern     notMatch Pattern   Moreover regarding a pattern   A-Z   all characters included from A to Z  a-z   all characters included from a to z  0 9   all characters included from 0 to 9   Therefore it will substitute all the char NOT included in the pattern

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Java s regular expressions don t require you to put a forward-slash     or any other delimiter around the regex  as opposed to other languages like Perl  for example

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You could also try this simpler regex    str   str replaceAll    P Alnum

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public static void main String   args        String value     Chlamydia spp  IgG  IgM  amp  IgA Abs  8006          System out println value replaceAll    A-Za-z0-9               output  ChlamydiasppIgGIgMIgAAbs8006  Github  https   github com AlbinViju Learning blob master StripNonAlphaNumericFromString java

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Simple method   public boolean isBlank String value        return  value    null    value equals        value equals  null      value trim   equals          public String normalizeOnlyLettersNumbers String str        if   isBlank str             return str replaceAll      p L   p Nd                 else           return

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If you want to also allow alphanumeric characters which don t belong to the ascii characters set  like for instance german umlaut s  you can consider using the following solution    String value    your value        this could be placed as a static final constant  so the compiling is only done once  Pattern pattern   Pattern compile      w    Pattern UNICODE CHARACTER CLASS     value   pattern matcher value  replaceAll        Please note that the usage of the UNICODE CHARACTER CLASS flag could have an impose on performance penalty  see javadoc of this flag

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Try   return value replaceAll    A-Za-z0-9           or  return value replaceAll     W

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You should be aware that   a-zA-Z  will replace characters not being itself in the character range A-Z a-z  That means special characters like        etc  or cyrillic characters and such will be removed    If the replacement of these characters is not wanted use pre-defined character classes  instead    str replaceAll      p IsAlphabetic   p IsDigit            PS   p Alnum  does not achieve this effect  it acts the same as  A-Za-z0-9

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Guava s CharMatcher provides a concise solution   output   CharMatcher javaLetterOrDigit   retainFrom input

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Using Guava you can easily combine different type of criteria  For your specific solution you can use   value   CharMatcher inRange  0    9            or CharMatcher inRange  a    z            or CharMatcher inRange  A    Z     retainFrom value

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I made this method for creating filenames   public static String safeChar String input        char   allowed    0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ-   toCharArray        char   charArray   input toString   toCharArray        StringBuilder result   new StringBuilder        for  char c   charArray                for  char a   allowed                        if c  a  result append a                       return result toString

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Use   A-Za-z0-9     Note  removed the space since that is not typically considered alphanumeric

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return value replaceAll    A-Za-z0-9            This will leave spaces intact  I assume that s what you want  Otherwise  remove the space from the regex

[java] Replacing all non-alphanumeric characters with empty strings

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