Length of the String without using length method

Question

How can I find the length of a String without using the length   method of String class

User · Answer

try below code      public static int Length String str        str   str     0       int count   0       for  int i   0  str charAt i       0   i              count               return count

User · Answer

For the semi-best methods have been posted and there s nothing better then String length     Redirect System out to a FileOutputStream  use System out print  not println     to print the string and get the file size - this is equal to the string length  Don t forget to restore System out after the measurement    -

User · Answer

Since nobody s posted the naughty back door way yet   public int getLength String arg      Field count   String class getDeclaredField  count      count setAccessible true     may throw security exception in  real  environment   return count getInt arg

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You can use a loop to check every character position and catch the IndexOutOfBoundsException when you pass the last character  But why   public int slowLength String myString        int i   0      try           while  true                myString charAt i               i                    catch  IndexOutOfBoundsException e           return i            Note  This is very bad programming practice and very inefficient   You can use reflection to examine the internal variables in the String class  specifically count

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Hidden length   usage       String s    foobar        int i   0      for char c  s toCharArray                  i

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str toCharArray   length should work  Or how about   str lastIndexOf      Probably even runs in constant time    Another one  Matcher m   Pattern compile      matcher str   m find    int length   m end     One of the dumbest solutions  str split     length - 1 Is this cheating  new StringBuilder str  length     -

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Here s another way   int length   0  while   str equals            str   str substring 1         length      In the same spirit  although much less efficient    String regex      s    int length   0  while   str matches regex         regex               length      Or even   int length   0  while   str matches    s       length                 length

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Very nice solutions   Here are some more   int length   String s          int length   0           iterate through all possible code points      for   int i   INTEGER   MIN VALUE   i  lt   INTEGER   MAX VALUE   i                            count the number of i s in the string           for   int next   s   indexOf   i   next     1   next    -1   next   s   indexOf   i   next     1                              length                              return   length         Here is a recursive version   int length   String s          int length   0        search        for   int i   Integer   MIN VALUE   i  lt   Integer   MAX VALUE   i                       final int k   s   indexOf   i               if   k    -1                              length   length   s   substring   0   k       length   s   substring   k                      break search                           return   length         And still more  int length   String s          int length        search        for   length   0   true   length                       int     codePoints   new int   length               for   each possible value of codePoints from  MIN VALUE MIN VALUE      to  MAX VALUE MAX VALUE                                   if   new String   codePoints     equals   s       break search                            How could I forget one that actually works in a reasonable time   String length is still preferred    int length   String s          String t   s   replaceAll          A           int length        String r             search        for   r        length   0   true   r     A    length                                 if   r   equals   t                                          break search                                     return   length

User · Answer

We can iterate through the string like a character array  and count that way  A much more down to earth way of doing it    String s    foo  char arr   s toCharArray    int len   0  for char single   arr     len        Using the  foreach  version of the for loop

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Just to complete this with the most stupid method I can come up with  Generate all possible strings of length 1  use equals to compare them to the original string  if they are equal  the string length is 1  If no string matches  generate all possible strings of length 2  compare them  for string length 2  Etc  Continue until you find the string length or the universe ends  whatever happens first

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This is a complete program you can compile and run it   import java util Scanner   class Strlen       public static void main String   args           Scanner sc   new Scanner System in           System out print   nEnter Your Name   gt                   String ab   sc nextLine            System out println   nName Length is    len ab               public static int len String ab           char   ac   ab toCharArray            int i   0  k   0           try              for i 0 k 0 ac i     0  i                    k                      catch Exception e                     return k

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Even more slower one  public int slowerLength String myString    String   str   myString split      int lol 0  for String s str       lol      return  lol-1      Or even slower   public int slowerLength String myString    String   str   myString split      int lol 0  for String s str       lol    s toCharArray   length    return lol

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String blah    HellO   int count   0  for  char c   blah toCharArray          count      System out println  blah s length      count

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Just for completeness  and this is not at all recommended    int length  try      length   str getBytes  UTF-16BE   length   2   catch  UnsupportedEncodingException e       throw new AssertionError  Cannot happen  UTF-16BE is always a supported encoding        This works because a char is a UTF-16 code unit  and str length   returns the number of such code units  Each UTF-16 code unit takes up 2 bytes  so we divide by 2  Additionally  there is no byte order mark written with UTF-16BE

[java] Length of the String without using length() method

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