How to determine if a String has non-alphanumeric characters

Question

I need a method that can tell me if a String has non alphanumeric characters   For example if the String is  abcdef   or  abcdef     the method must return true

User · Answer

If you can use the Apache Commons library  then Commons-Lang StringUtils has a method called isAlphanumeric   that does what you re looking for

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One approach is to do that using the String class itself  Let s say that your string is something like that   String s    some text   boolean hasNonAlpha   s matches       a-zA-Z0-9           one other is to use an external library  such as Apache commons   String s    some text   boolean hasNonAlpha    StringUtils isAlphanumeric s

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Use this function to check if a string is alphanumeric   public boolean isAlphanumeric String str        char   charArray   str toCharArray        for char c charArray                if   Character isLetterOrDigit c               return false            return true      It saves having to import external libraries and the code can easily be modified should you later wish to perform different validation checks on strings

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You have to go through each character in the String and check Character isDigit char   or Character isletter char    Alternatively  you can use regex

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Though it won t work for numbers  you can check if the lowercase and uppercase values are same or not  For non-alphabetic characters they will be same  You should check for number before this for better usability

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string matches     W      should do what you want  but it does not include whitespace  string matches        W   s       does match whitespace as well

User · Answer

Using Apache Commons Lang    StringUtils isAlphanumeric String    Alternativly iterate over String s characters and check with    Character isLetterOrDigit char    You ve still one problem left  Your example string  abcdef    is alphanumeric  since    is a letter  But I think you want it to be considered non-alphanumeric  right    So you may want to use regular expression instead   String s    abcdef     Pattern p   Pattern compile    a-zA-Z0-9     boolean hasSpecialChar   p matcher s  find

User · Answer

You can use isLetter char c  static method of Character class in Java lang    public boolean isAlpha String s        char   charArr   s toCharArray         for char c   charArr            if  Character isLetter c                 return false                      return true

[java] How to determine if a String has non-alphanumeric characters?

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