Check if a String contains a special character

Question

How do you check if a String contains a special character like                       gt

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This is tested in android 7 0 up to android 10 0 and it works  Use this code to check if string contains special character and numbers     name   firstname getText   toString      name is the variable that holds the string value    Pattern special  Pattern compile    a-z0-9     Pattern CASE INSENSITIVE     Pattern number   Pattern compile   0-9    Pattern CASE INSENSITIVE     Matcher matcher   special matcher name     Matcher matcherNumber   number matcher name      boolean constainsSymbols   matcher find      boolean containsNumber   matcherNumber find       if constainsSymbols    true        string contains special symbol character       else if containsNumber    true        string contains numbers       else       string doesn t contain special characters or numbers

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Have a look at the java lang Character class  It has some test methods and you may find one that fits your needs   Examples  Character isSpaceChar c  or  Character isJavaLetter c

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All depends on exactly what you mean by  special   In a regex you can specify    W  to mean non-alpahnumeric  p Punct  to mean punctuation characters   I suspect that the latter is what you mean  But if not use a    list to specify exactly what you want

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Convert the string into char array with all the letters in lower case   char c     str toLowerCase   toCharArray      Then you can use Character isLetterOrDigit c index   to find out which index has special characters

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First you have to exhaustively identify the special characters that you want to check   Then you can write a regular expression and use   public boolean matches String regex

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this is updated version of code that i posted    The isValidName Method will check whether the name passed as argument should not contain- 1 null value or space 2 any special character 3 Digits  0-9  Explanation--- Here str2 is String array variable which stores the the splited string of name that is passed as argument The count variable will count the number of special character occurs The method will return true if it satisfy all the condition     public boolean isValidName String name        String specialCharacters        amp       -     lt   gt            0123456789       String str2   name split          int count 0      for  int i 0 i lt str2 length i                  if  specialCharacters contains str2 i                          count                                if  name  null  amp  amp  count  0                 return true            else               return false

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without using regular expression              String specialCharacters        amp       -     lt   gt            0123456789       String name  3  saroj        String str2   name split           for  int i 0 i lt str2 length i              if  specialCharacters contains str2 i                  System out println  true              break            else         System out println  false

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in the line String str2   name split      give an extra character in Array     Let me explain by example  Aditya  split     would return    A  d i t y a  You will have a extra character in your Array    The  Aditya  split     does not work as expected by saroj routray you will get an extra character in String       A  d i t y a     I have modified it see below code it work as expected    public static boolean isValidName String inputString         String specialCharacters          amp       -     lt   gt            0123456789       String   strlCharactersArray   new String inputString length         for  int i   0  i  lt  inputString length    i               strlCharactersArray i    Character              toString inputString charAt i                now  strlCharactersArray i   A  d  i  t  y  a      int count   0      for  int i   0  i  lt   strlCharactersArray length  i              if  specialCharacters contains  strlCharactersArray i                  count                          if  inputString    null  amp  amp  count    0            return true        else           return false

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Pattern p   Pattern compile    a-z0-9     Pattern CASE INSENSITIVE   Matcher m   p matcher  I am a string    boolean b   m find     if  b     System out println  There is a special character in my string

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This worked for me   String s    string   if  Pattern matches   a-zA-Z     s      System out println  clear      else    System out println  buzz

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You can use the following code to detect special character from string   import java util regex Matcher  import java util regex Pattern   public class DetectSpecial   public int getSpecialCharacterCount String s         if  s    null    s trim   isEmpty               System out println  Incorrect format of string             return 0              Pattern p   Pattern compile    A-Za-z0-9          Matcher m   p matcher s          boolean b   m matches         boolean b   m find         if  b          System out println  There is a special character in my string          else          System out println  There is no special char          return 0

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If you want to have LETTERS  SPECIAL CHARACTERS and NUMBERS in your password with at least 8 digit  then use this code  it is working perfectly  public static boolean Password Validation String password          if password length   gt  8                Pattern letter   Pattern compile   a-zA-z             Pattern digit   Pattern compile   0-9             Pattern special   Pattern compile          amp         lt  gt           -               Pattern eight   Pattern compile     8                  Matcher hasLetter   letter matcher password              Matcher hasDigit   digit matcher password              Matcher hasSpecial   special matcher password               return hasLetter find    amp  amp  hasDigit find    amp  amp  hasSpecial find               else         return false

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Visit each character in the string to see if that character is in a blacklist of special characters  this is O n m    The pseudo-code is   for each char in string    if char in blacklist            The complexity can be slightly improved by sorting the blacklist so that you can early-exit each check   However  the string find function is probably native code  so this optimisation - which would be in Java byte-code - could well be slower

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If it matches regex  a-zA-Z0-9    then there is not special characters in it

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What do you exactly call  special character    If you mean something like  anything that is not alphanumeric  you can use org apache commons lang StringUtils class  methods IsAlpha IsNumeric IsWhitespace IsAsciiPrintable    If it is not so trivial  you can use a regex that defines the exact character list you accept and match the string against it

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Pattern p   Pattern compile     p Alpha      p Punct     p Alpha               Matcher m   p matcher  Afsff esfsf098            boolean b   m matches             if  b    true             System out println  There is a sp  character in my string            else             System out println  There is no sp  char

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Use java util regex Pattern class s static method  matches regex  String obj  regex   characters in lower and upper case  amp  digits between 0-9  String obj   String object you want to check either it contain special character or not  It returns boolean value true if only contain characters and numbers  otherwise returns boolean value false Example   String isin    12GBIU34RT12   lt br gt  if Pattern matches   a-zA-Z0-9     isin  lt br gt   lt br gt      amp nbsp   amp nbsp   amp nbsp   amp nbsp System out println  Valid isin    lt br gt   else  lt br gt      amp nbsp   amp nbsp   amp nbsp   amp nbsp System out println  Invalid isin    lt br gt

[java] Check if a String contains a special character

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