Checking whether a String contains a number value in Java

Question

How can I write a method to find whether a given string contains a number  The method should return true if the string contains a number and false otherwise

User · Answer

Why don t you try to write a function based on Integer parseInt String obj    The function could accept as parameter your String object  and then tokenize the String and use Integer parseInt String obj  to extract the number from the  lucky  substring     Javadoc of Integer parseInt String obj

User · Answer

Using a loop -  public static boolean containsDigit final String aString        if  aString    null  amp  amp   aString isEmpty                  for  char c   aString toCharArray                          if  Character isDigit c                                 return true                                     return false      Using a stream -  public static boolean containsDigit final String aString        return aString    null  amp  amp   aString isEmpty    amp  amp              aString chars   anyMatch Character  isDigit

User · Answer

if str matches      d             contains a number   else        does not contain a number     Previous suggested solution  which does not work  but brought back because of  Eng Fouad s request suggestion   Not working suggested solution  String strWithNumber    This string has a 1 number   String strWithoutNumber    This string does not have a number    System out println strWithNumber contains   d     System out println strWithoutNumber contains   d       Working solution  String strWithNumber    This string has a 1 number   if strWithNumber matches      d           System out println     strWithNumber    contains digit      else      System out println     strWithNumber    does not contain a digit       String strWithoutNumber    This string does not have a number   if strWithoutNumber matches      d           System out println     strWithoutNumber    contains digit      else      System out println     strWithoutNumber    does not contain a digit        Output   This string has a 1 number  contains digit  This string does not have a number  does not contain a digit

User · Answer

try        Integer parseInt string         return true   catch  Exception  e         return false      or you can do it himself    for   int i   0  i  lt  string length    i           if      string i   gt    0     string i   lt    9                 return false      return true    Of course is also function isDigit

User · Answer

You could use a regex to find out if the String contains a number  Take a look at the matches   method

User · Answer

Another possible solution is to use a Scanner object like this   Scanner scanner   new Scanner inputString     if  scanner hasNextInt          return true    else     return false     Of course  if you are looking for a double  use hasNextDouble   method  see  Scanner javadoc

User · Answer

Shef s answer doesn t compile for me  It looks like he s using RegEx in String contains    If you want to use RegEx use this   String strWithNumber    This string has a 1 number   String strWithoutNumber    This string has a number    System out println strWithNumber matches      d       System out println strWithoutNumber matches      d

User · Answer

Looks like people like doing spoonfeeding  so I have decided to post the worst solution to an easy task   public static boolean isNumber String s  throws Exception       boolean result   false      byte   bytes   s getBytes  ASCII        int tmp  i   bytes length      while  i  gt 0   amp  amp   result     tmp   bytes --i  -  0    gt   0   amp  amp  tmp  lt   9        return result      About the worst code I could imagine  but there might be other people here who can come up with even worse solutions   Hm  containsNumber is worse   public static boolean containsNumber String s  throws Exception       boolean result   false      byte   bytes   s getBytes  ASCII        int tmp  i   bytes length      while  i  gt 0   amp  amp   true    result      tmp   bytes --i  -  0    gt   0   amp  amp  tmp  lt   9         return result

[java] Checking whether a String contains a number value in Java

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