Check if String contains only letters

Question

The idea is to have a String read and to verify that it does not contain any numeric characters  So something like  smith23  would not be acceptable

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public boolean isAlpha String name        String s name toLowerCase        for int i 0  i lt s length   i                  if  s charAt i  gt   a   amp  amp  s charAt i  lt   z                          continue                    else                      return false                      return true

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Or if you are using Apache Commons   StringUtils isAlpha

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I used this regex expression      a-zA-Z        With if not statement it will avoid all expressions that have a letter before  at the end or between any type of other character   String strWithLetters    123AZ456   if   Pattern matches     a-zA-Z       str1    return true  else return false

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A quick way to do it is by   public boolean isStringAlpha String aString        int charCount   0      String alphabet    ABCDEFGHIJKLMNOPQRSTUVWXYZ        if  aString length      0            return false    zero length string ain t alpha            for  int i   0  i  lt  aString length    i              for  int j   0  j  lt  alphabet length    j                  if  aString substring i  i   1  equals alphabet substring j  j   1                          aString substring i  i   1  equals alphabet substring j  j   1  toLowerCase                       charCount                                     if  charCount     i   1                 System out println   n  Invalid input  Enter alpha values   n                return false                       return true      Because you don t have to run the whole aString to check if it isn t an alpha String

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Try using regular expressions  String matches

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First import Pattern    import java util regex Pattern    Then use this simple code   String s    smith23   if  Pattern matches   a-zA-Z    s           Do something   System out println  Yes  string contains letters only     else    System out println  Nope  Other characters detected            This will output      Nope  Other characters detected

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Faster way is below  Considering letters are only a-z A-Z   public static void main  String   args             System out println bestWay  azAZpratiyushkumarsinghjdnfkjsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa             System out println isAlpha  azAZpratiyushkumarsinghjdnfkjsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa              System out println bestWay  azAZpratiyushkumarsinghjdnfkjsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa             System out println isAlpha  azAZpratiyushkumarsinghjdnfkjsaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa1aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa                public static boolean bettertWay String name            char   chars   name toCharArray            long startTimeOne   System nanoTime            for char c   chars               if   c gt  65  amp  amp  c lt  90  amp  amp   c gt  97  amp  amp  c lt  122                     System out println System nanoTime   - startTimeOne                       return false                                  System out println System nanoTime   - startTimeOne           return true              public static boolean isAlpha String name            char   chars   name toCharArray            long startTimeOne   System nanoTime            for  char c   chars                if  Character isLetter c                     System out println System nanoTime   - startTimeOne                   return false                                  System out println System nanoTime   - startTimeOne           return true          Runtime is calculated in nano seconds  It may vary system to system   5748  bettertWay without numbers true 89493   isAlpha without  numbers true 3284   bettertWay with numbers false 22989   isAlpha with numbers false

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Java 8 lambda expressions  Both fast and simple   boolean allLetters   someString chars   allMatch Character  isLetter

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String expression      a-zA-Z              CharSequence inputStr   str          Pattern pattern   Pattern compile expression           Matcher matcher   pattern matcher inputStr           if matcher matches                              if pattern matches                    else                          if pattern does not matches

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What do you want  Speed or simplicity  For speed  go for a loop based approach  For simplicity  go for a one liner RegEx based approach   Speed  public boolean isAlpha String name        char   chars   name toCharArray         for  char c   chars            if  Character isLetter c                 return false                       return true      Simplicity  public boolean isAlpha String name        return name matches   a-zA-Z

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While there are many ways to skin this cat  I prefer to wrap such code into reusable extension methods that make it trivial to do going forward   When using extension methods  you can also avoid RegEx as it is slower than a direct character check   I like using the extensions in the Extensions cs NuGet package   It makes this check as simple as   Add the https   www nuget org packages Extensions cs package to your project  Add  quot using Extensions  quot  to the top of your code   quot smith23 quot  IsAlphabetic   will return False whereas  quot john smith quot  IsAlphabetic   will return True   By default the  IsAlphabetic   method ignores spaces  but it can also be overridden such that  quot john smith quot  IsAlphabetic false  will return False since the space is not considered part of the alphabet  Every other check in the rest of the code is simply MyString IsAlphabetic

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Check this i guess this is help you because it s work in my project so once you check this code  if   Pattern matches     a-zA-Z     a-zA-Z    str1         String not contain only character     else      String contain only character

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private boolean isOnlyLetters String s       char c          boolean isGood false  safe isGood      int failCount 0      for int i 0 i lt s length   i             c   s charAt i           if Character isLetter c               isGood true          else              isGood false              failCount  1                      if failCount  0  amp  amp  s length   gt 0          safe true      else         safe false      return safe      I know it s a bit crowded  I was using it with my program and felt the desire to share it with people  It can tell if any character in a string is not a letter or not  Use it if you want something easy to clarify and look back on

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Use StringUtils isAlpha   method and it will make your life simple

[java] Check if String contains only letters

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