What is the easiest best most correct way to iterate through the characters of a string in Java

Question

StringTokenizer  Convert the String to a char   and iterate over that  Something else

User · Answer

If you need to iterate through the code points of a String (see this answer) a shorter / more readable way is to use the CharSequence#codePoints method added in Java 8:

for(int c : string.codePoints().toArray()){
    ...
}

or using the stream directly instead of a for loop:

string.codePoints().forEach(c -> ...);

There is also CharSequence#chars if you want a stream of the characters (although it is an IntStream, since there is no CharStream).

User · Answer

I agree that StringTokenizer is overkill here  Actually I tried out the suggestions above and took the time    My test was fairly simple  create a StringBuilder with about a million characters  convert it to a String  and traverse each of them with charAt     after converting to a char array   with a CharacterIterator a thousand times  of course making sure to do something on the string so the compiler can t optimize away the whole loop  -      The result on my 2 6 GHz Powerbook  that s a mac  -    and JDK 1 5    Test 1  charAt   String --  3138msec Test 2  String converted to array --  9568msec  Test 3  StringBuilder charAt --  3536msec  Test 4  CharacterIterator and String --  12151msec   As the results are significantly different  the most straightforward way also seems to be the fastest one  Interestingly  charAt   of a StringBuilder seems to be slightly slower than the one of String   BTW I suggest not to use CharacterIterator as I consider its abuse of the   uFFFF  character as  end of iteration  a really awful hack  In big projects there s always two guys that use the same kind of hack for two different purposes and the code crashes really mysteriously    Here s one of the tests       int count   1000               System out println  Test 1  charAt   String        long t   System currentTimeMillis        int sum 0      for  int i 0  i lt count  i              int len   str length            for  int j 0  j lt len  j                  if  str charAt j      b                   sum   sum   1                      t   System currentTimeMillis  -t      System out println  result     sum     after     t    msec

User · Answer

I agree that StringTokenizer is overkill here  Actually I tried out the suggestions above and took the time    My test was fairly simple  create a StringBuilder with about a million characters  convert it to a String  and traverse each of them with charAt     after converting to a char array   with a CharacterIterator a thousand times  of course making sure to do something on the string so the compiler can t optimize away the whole loop  -      The result on my 2 6 GHz Powerbook  that s a mac  -    and JDK 1 5    Test 1  charAt   String --  3138msec Test 2  String converted to array --  9568msec  Test 3  StringBuilder charAt --  3536msec  Test 4  CharacterIterator and String --  12151msec   As the results are significantly different  the most straightforward way also seems to be the fastest one  Interestingly  charAt   of a StringBuilder seems to be slightly slower than the one of String   BTW I suggest not to use CharacterIterator as I consider its abuse of the   uFFFF  character as  end of iteration  a really awful hack  In big projects there s always two guys that use the same kind of hack for two different purposes and the code crashes really mysteriously    Here s one of the tests       int count   1000               System out println  Test 1  charAt   String        long t   System currentTimeMillis        int sum 0      for  int i 0  i lt count  i              int len   str length            for  int j 0  j lt len  j                  if  str charAt j      b                   sum   sum   1                      t   System currentTimeMillis  -t      System out println  result     sum     after     t    msec

User · Answer

I agree that StringTokenizer is overkill here  Actually I tried out the suggestions above and took the time    My test was fairly simple  create a StringBuilder with about a million characters  convert it to a String  and traverse each of them with charAt     after converting to a char array   with a CharacterIterator a thousand times  of course making sure to do something on the string so the compiler can t optimize away the whole loop  -      The result on my 2 6 GHz Powerbook  that s a mac  -    and JDK 1 5    Test 1  charAt   String --  3138msec Test 2  String converted to array --  9568msec  Test 3  StringBuilder charAt --  3536msec  Test 4  CharacterIterator and String --  12151msec   As the results are significantly different  the most straightforward way also seems to be the fastest one  Interestingly  charAt   of a StringBuilder seems to be slightly slower than the one of String   BTW I suggest not to use CharacterIterator as I consider its abuse of the   uFFFF  character as  end of iteration  a really awful hack  In big projects there s always two guys that use the same kind of hack for two different purposes and the code crashes really mysteriously    Here s one of the tests       int count   1000               System out println  Test 1  charAt   String        long t   System currentTimeMillis        int sum 0      for  int i 0  i lt count  i              int len   str length            for  int j 0  j lt len  j                  if  str charAt j      b                   sum   sum   1                      t   System currentTimeMillis  -t      System out println  result     sum     after     t    msec

User · Answer

If you have Guava on your classpath  the following is a pretty readable alternative  Guava even has a fairly sensible custom List implementation for this case  so this shouldn t be inefficient   for char c   Lists charactersOf yourString            Do whatever you want          UPDATE  As  Alex noted  with Java 8 there s also CharSequence chars to use  Even the type is IntStream  so it can be mapped to chars like   yourString chars            mapToObj c - gt  Character valueOf  char  c            forEach c - gt  System out println c       Or whatever you want

User · Answer

This Example Code will Help you out   import java util Comparator  import java util HashMap  import java util Map  import java util TreeMap   public class Solution       public static void main String   args            HashMap lt String  Integer gt  map   new HashMap lt String  Integer gt             map put  a   10           map put  b   30           map put  c   50           map put  d   40           map put  e   20           System out println map            Map sortedMap   sortByValue map           System out println sortedMap              public static Map sortByValue Map unsortedMap            Map sortedMap   new TreeMap new ValueComparator unsortedMap            sortedMap putAll unsortedMap           return sortedMap            class ValueComparator implements Comparator       Map map       public ValueComparator Map map            this map   map             public int compare Object keyA  Object keyB            Comparable valueA    Comparable  map get keyA           Comparable valueB    Comparable  map get keyB           return valueB compareTo valueA

User · Answer

I use a for loop to iterate the string and use charAt   to get each character to examine it   Since the String is implemented with an array  the charAt   method is a constant time operation   String s       stuff       for  int i   0  i  lt  s length    i         char c   s charAt i                 Process char     That s what I would do   It seems the easiest to me   As far as correctness goes  I don t believe that exists here   It is all based on your personal style

User · Answer

StringTokenizer is totally unsuited to the task of breaking a string into its individual characters   With String split   you can do that easily by using a regex that matches nothing  e g    String   theChars   str split         But StringTokenizer doesn t use regexes  and there s no delimiter string you can specify that will match the nothing between characters   There is one cute little hack you can use to accomplish the same thing  use the string itself as the delimiter string  making every character in it a delimiter  and have it return the delimiters   StringTokenizer st   new StringTokenizer str  str  true     However  I only mention these options for the purpose of dismissing them   Both techniques break the original string into one-character strings instead of char primitives  and both involve a great deal of overhead in the form of object creation and string manipulation   Compare that to calling charAt   in a for loop  which incurs virtually no overhead

User · Answer

I agree that StringTokenizer is overkill here  Actually I tried out the suggestions above and took the time    My test was fairly simple  create a StringBuilder with about a million characters  convert it to a String  and traverse each of them with charAt     after converting to a char array   with a CharacterIterator a thousand times  of course making sure to do something on the string so the compiler can t optimize away the whole loop  -      The result on my 2 6 GHz Powerbook  that s a mac  -    and JDK 1 5    Test 1  charAt   String --  3138msec Test 2  String converted to array --  9568msec  Test 3  StringBuilder charAt --  3536msec  Test 4  CharacterIterator and String --  12151msec   As the results are significantly different  the most straightforward way also seems to be the fastest one  Interestingly  charAt   of a StringBuilder seems to be slightly slower than the one of String   BTW I suggest not to use CharacterIterator as I consider its abuse of the   uFFFF  character as  end of iteration  a really awful hack  In big projects there s always two guys that use the same kind of hack for two different purposes and the code crashes really mysteriously    Here s one of the tests       int count   1000               System out println  Test 1  charAt   String        long t   System currentTimeMillis        int sum 0      for  int i 0  i lt count  i              int len   str length            for  int j 0  j lt len  j                  if  str charAt j      b                   sum   sum   1                      t   System currentTimeMillis  -t      System out println  result     sum     after     t    msec

User · Answer

In Java 8 we can solve it as  String str    quot xyz quot   str chars   forEachOrdered i - gt  System out print  char i    str codePoints   forEachOrdered i - gt  System out print  char i     The method chars   returns an IntStream as mentioned in doc   Returns a stream of int zero-extending the char values from this sequence  Any char which maps to a surrogate code point is passed through uninterpreted  If the sequence is mutated while the stream is being read  the result is undefined   The method codePoints   also returns an IntStream as per doc   Returns a stream of code point values from this sequence  Any surrogate pairs encountered in the sequence are combined as if by Character toCodePoint and the result is passed to the stream  Any other code units  including ordinary BMP characters  unpaired surrogates  and undefined code units  are zero-extended to int values which are then passed to the stream   How is char and code point different  As mentioned in this article   Unicode 3 1 added supplementary characters  bringing the total number of characters to more than the 2 16   65536 characters that can be distinguished by a single 16-bit char  Therefore  a char value no longer has a one-to-one mapping to the fundamental semantic unit in Unicode  JDK 5 was updated to support the larger set of character values  Instead of changing the definition of the char type  some of the new supplementary characters are represented by a surrogate pair of two char values  To reduce naming confusion  a code point will be used to refer to the number that represents a particular Unicode character  including supplementary ones   Finally why forEachOrdered and not forEach   The behaviour of forEach is explicitly nondeterministic where as the forEachOrdered performs an action for each element of this stream  in the encounter order of the stream if the stream has a defined encounter order  So forEach does not guarantee that the order would be kept  Also check this question for more  For difference between a character  a code point  a glyph and a grapheme check this question

User · Answer

I wouldn t use StringTokenizer as it is one of classes in the JDK that s legacy   The javadoc says      StringTokenizer is a legacy class that   is retained for compatibility reasons   although its use is discouraged in new   code  It is recommended that anyone   seeking this functionality use the   split  method of String or the   java util regex package instead

User · Answer

See The Java Tutorials  Strings   public class StringDemo       public static void main String   args            String palindrome    Dot saw I was Tod           int len   palindrome length            char   tempCharArray   new char len           char   charArray   new char len               put original string in an array of chars         for  int i   0  i  lt  len  i                  tempCharArray i    palindrome charAt i                          reverse array of chars         for  int j   0  j  lt  len  j                  charArray j    tempCharArray len - 1 - j                      String reversePalindrome    new String charArray           System out println reversePalindrome             Put the length into int len and use for loop

User · Answer

Two options  for int i   0  n   s length     i  lt  n   i           char c   s charAt i        or  for char c   s toCharArray             process c     The first is probably faster  then 2nd is probably more readable

User · Answer

In Java 8 we can solve it as  String str    quot xyz quot   str chars   forEachOrdered i - gt  System out print  char i    str codePoints   forEachOrdered i - gt  System out print  char i     The method chars   returns an IntStream as mentioned in doc   Returns a stream of int zero-extending the char values from this sequence  Any char which maps to a surrogate code point is passed through uninterpreted  If the sequence is mutated while the stream is being read  the result is undefined   The method codePoints   also returns an IntStream as per doc   Returns a stream of code point values from this sequence  Any surrogate pairs encountered in the sequence are combined as if by Character toCodePoint and the result is passed to the stream  Any other code units  including ordinary BMP characters  unpaired surrogates  and undefined code units  are zero-extended to int values which are then passed to the stream   How is char and code point different  As mentioned in this article   Unicode 3 1 added supplementary characters  bringing the total number of characters to more than the 2 16   65536 characters that can be distinguished by a single 16-bit char  Therefore  a char value no longer has a one-to-one mapping to the fundamental semantic unit in Unicode  JDK 5 was updated to support the larger set of character values  Instead of changing the definition of the char type  some of the new supplementary characters are represented by a surrogate pair of two char values  To reduce naming confusion  a code point will be used to refer to the number that represents a particular Unicode character  including supplementary ones   Finally why forEachOrdered and not forEach   The behaviour of forEach is explicitly nondeterministic where as the forEachOrdered performs an action for each element of this stream  in the encounter order of the stream if the stream has a defined encounter order  So forEach does not guarantee that the order would be kept  Also check this question for more  For difference between a character  a code point  a glyph and a grapheme check this question

User · Answer

Elaborating on this answer and this answer   Above answers point out the problem of many of the solutions here which don t iterate by code point value -- they would have trouble with any surrogate chars  The java docs also outline the issue here  see  Unicode Character Representations     Anyhow  here s some code that uses some actual surrogate chars from the supplementary Unicode set  and converts them back to a String   Note that  toChars   returns an array of chars   if you re dealing with surrogates  you ll necessarily have two chars   This code should work for any Unicode character       String supplementary    Some Supplementary         supplementary codePoints   forEach cp - gt               System out print new String Character toChars cp

User · Answer

I wouldn t use StringTokenizer as it is one of classes in the JDK that s legacy   The javadoc says      StringTokenizer is a legacy class that   is retained for compatibility reasons   although its use is discouraged in new   code  It is recommended that anyone   seeking this functionality use the   split  method of String or the   java util regex package instead

User · Answer

See The Java Tutorials  Strings   public class StringDemo       public static void main String   args            String palindrome    Dot saw I was Tod           int len   palindrome length            char   tempCharArray   new char len           char   charArray   new char len               put original string in an array of chars         for  int i   0  i  lt  len  i                  tempCharArray i    palindrome charAt i                          reverse array of chars         for  int j   0  j  lt  len  j                  charArray j    tempCharArray len - 1 - j                      String reversePalindrome    new String charArray           System out println reversePalindrome             Put the length into int len and use for loop

User · Answer

Note most of the other techniques described here break down if you re dealing with characters outside of the BMP  Unicode Basic Multilingual Plane   i e  code points that are outside of the u0000-uFFFF range  This will only happen rarely  since the code points outside this are mostly assigned to dead languages  But there are some useful characters outside this  for example some code points used for mathematical notation  and some used to encode proper names in Chinese   In that case your code will be   String str           int offset   0  strLen   str length    while  offset  lt  strLen      int curChar   str codePointAt offset     offset    Character charCount curChar        do something with curChar     The Character charCount int  method requires Java 5    Source  http   mindprod com jgloss codepoint html

User · Answer

I wouldn t use StringTokenizer as it is one of classes in the JDK that s legacy   The javadoc says      StringTokenizer is a legacy class that   is retained for compatibility reasons   although its use is discouraged in new   code  It is recommended that anyone   seeking this functionality use the   split  method of String or the   java util regex package instead

User · Answer

So typically there are two ways to iterate through string in java which has already been answered by multiple people here in this thread  just adding my version of it First is using   String s   sc next      assuming scanner class is defined above for int i 0  i lt s length  i          s charAt i       This being the first way and is a constant time operation will hardly add any overhead      char   str   new char 10   str   s toCharArray      this is another way of doing so and it takes O n  amount of time for copying contents from your string class to character array   If performance is at stake then I will recommend to use the first one in constant time  if it is not then going with the second one makes your work easier considering the immutability with string classes in java

User · Answer

See The Java Tutorials  Strings   public class StringDemo       public static void main String   args            String palindrome    Dot saw I was Tod           int len   palindrome length            char   tempCharArray   new char len           char   charArray   new char len               put original string in an array of chars         for  int i   0  i  lt  len  i                  tempCharArray i    palindrome charAt i                          reverse array of chars         for  int j   0  j  lt  len  j                  charArray j    tempCharArray len - 1 - j                      String reversePalindrome    new String charArray           System out println reversePalindrome             Put the length into int len and use for loop

User · Answer

There are some dedicated classes for this   import java text     final CharacterIterator it   new StringCharacterIterator s   for char c   it first    c    CharacterIterator DONE  c   it next            process c

User · Answer

If you need performance  then you must test on your environment  No other way   Here example code   int tmp   0  String s   new String new byte 64 1024          long st   System nanoTime        for int i   0  n   s length    i  lt  n  i              tmp    s charAt i             st   System nanoTime   - st      System out println  1     st            long st   System nanoTime        char   ch   s toCharArray        for int i   0  n   ch length  i  lt  n  i              tmp    ch i             st   System nanoTime   - st      System out println  2     st           long st   System nanoTime        for char c   s toCharArray              tmp    c            st   System nanoTime   - st      System out println  3     st     System out println      tmp     On Java online I get   1 10349420 2 526130 3 484200 0   On Android x86 API 17 I get   1 9122107 2 13486911 3 12700778 0

User · Answer

StringTokenizer is totally unsuited to the task of breaking a string into its individual characters   With String split   you can do that easily by using a regex that matches nothing  e g    String   theChars   str split         But StringTokenizer doesn t use regexes  and there s no delimiter string you can specify that will match the nothing between characters   There is one cute little hack you can use to accomplish the same thing  use the string itself as the delimiter string  making every character in it a delimiter  and have it return the delimiters   StringTokenizer st   new StringTokenizer str  str  true     However  I only mention these options for the purpose of dismissing them   Both techniques break the original string into one-character strings instead of char primitives  and both involve a great deal of overhead in the form of object creation and string manipulation   Compare that to calling charAt   in a for loop  which incurs virtually no overhead

User · Answer

I use a for loop to iterate the string and use charAt   to get each character to examine it   Since the String is implemented with an array  the charAt   method is a constant time operation   String s       stuff       for  int i   0  i  lt  s length    i         char c   s charAt i                 Process char     That s what I would do   It seems the easiest to me   As far as correctness goes  I don t believe that exists here   It is all based on your personal style

User · Answer

This Example Code will Help you out   import java util Comparator  import java util HashMap  import java util Map  import java util TreeMap   public class Solution       public static void main String   args            HashMap lt String  Integer gt  map   new HashMap lt String  Integer gt             map put  a   10           map put  b   30           map put  c   50           map put  d   40           map put  e   20           System out println map            Map sortedMap   sortByValue map           System out println sortedMap              public static Map sortByValue Map unsortedMap            Map sortedMap   new TreeMap new ValueComparator unsortedMap            sortedMap putAll unsortedMap           return sortedMap            class ValueComparator implements Comparator       Map map       public ValueComparator Map map            this map   map             public int compare Object keyA  Object keyB            Comparable valueA    Comparable  map get keyA           Comparable valueB    Comparable  map get keyB           return valueB compareTo valueA

User · Answer

StringTokenizer is totally unsuited to the task of breaking a string into its individual characters   With String split   you can do that easily by using a regex that matches nothing  e g    String   theChars   str split         But StringTokenizer doesn t use regexes  and there s no delimiter string you can specify that will match the nothing between characters   There is one cute little hack you can use to accomplish the same thing  use the string itself as the delimiter string  making every character in it a delimiter  and have it return the delimiters   StringTokenizer st   new StringTokenizer str  str  true     However  I only mention these options for the purpose of dismissing them   Both techniques break the original string into one-character strings instead of char primitives  and both involve a great deal of overhead in the form of object creation and string manipulation   Compare that to calling charAt   in a for loop  which incurs virtually no overhead

User · Answer

Two options  for int i   0  n   s length     i  lt  n   i           char c   s charAt i        or  for char c   s toCharArray             process c     The first is probably faster  then 2nd is probably more readable

User · Answer

Note most of the other techniques described here break down if you re dealing with characters outside of the BMP  Unicode Basic Multilingual Plane   i e  code points that are outside of the u0000-uFFFF range  This will only happen rarely  since the code points outside this are mostly assigned to dead languages  But there are some useful characters outside this  for example some code points used for mathematical notation  and some used to encode proper names in Chinese   In that case your code will be   String str           int offset   0  strLen   str length    while  offset  lt  strLen      int curChar   str codePointAt offset     offset    Character charCount curChar        do something with curChar     The Character charCount int  method requires Java 5    Source  http   mindprod com jgloss codepoint html

User · Answer

There are some dedicated classes for this   import java text     final CharacterIterator it   new StringCharacterIterator s   for char c   it first    c    CharacterIterator DONE  c   it next            process c

User · Answer

If you need to iterate through the code points of a String (see this answer) a shorter / more readable way is to use the CharSequence#codePoints method added in Java 8:

for(int c : string.codePoints().toArray()){
    ...
}

or using the stream directly instead of a for loop:

string.codePoints().forEach(c -> ...);

There is also CharSequence#chars if you want a stream of the characters (although it is an IntStream, since there is no CharStream).

User · Answer

Note most of the other techniques described here break down if you re dealing with characters outside of the BMP  Unicode Basic Multilingual Plane   i e  code points that are outside of the u0000-uFFFF range  This will only happen rarely  since the code points outside this are mostly assigned to dead languages  But there are some useful characters outside this  for example some code points used for mathematical notation  and some used to encode proper names in Chinese   In that case your code will be   String str           int offset   0  strLen   str length    while  offset  lt  strLen      int curChar   str codePointAt offset     offset    Character charCount curChar        do something with curChar     The Character charCount int  method requires Java 5    Source  http   mindprod com jgloss codepoint html

User · Answer

Two options  for int i   0  n   s length     i  lt  n   i           char c   s charAt i        or  for char c   s toCharArray             process c     The first is probably faster  then 2nd is probably more readable

User · Answer

So typically there are two ways to iterate through string in java which has already been answered by multiple people here in this thread  just adding my version of it First is using   String s   sc next      assuming scanner class is defined above for int i 0  i lt s length  i          s charAt i       This being the first way and is a constant time operation will hardly add any overhead      char   str   new char 10   str   s toCharArray      this is another way of doing so and it takes O n  amount of time for copying contents from your string class to character array   If performance is at stake then I will recommend to use the first one in constant time  if it is not then going with the second one makes your work easier considering the immutability with string classes in java

User · Answer

Elaborating on this answer and this answer   Above answers point out the problem of many of the solutions here which don t iterate by code point value -- they would have trouble with any surrogate chars  The java docs also outline the issue here  see  Unicode Character Representations     Anyhow  here s some code that uses some actual surrogate chars from the supplementary Unicode set  and converts them back to a String   Note that  toChars   returns an array of chars   if you re dealing with surrogates  you ll necessarily have two chars   This code should work for any Unicode character       String supplementary    Some Supplementary         supplementary codePoints   forEach cp - gt               System out print new String Character toChars cp

User · Answer

If you need performance  then you must test on your environment  No other way   Here example code   int tmp   0  String s   new String new byte 64 1024          long st   System nanoTime        for int i   0  n   s length    i  lt  n  i              tmp    s charAt i             st   System nanoTime   - st      System out println  1     st            long st   System nanoTime        char   ch   s toCharArray        for int i   0  n   ch length  i  lt  n  i              tmp    ch i             st   System nanoTime   - st      System out println  2     st           long st   System nanoTime        for char c   s toCharArray              tmp    c            st   System nanoTime   - st      System out println  3     st     System out println      tmp     On Java online I get   1 10349420 2 526130 3 484200 0   On Android x86 API 17 I get   1 9122107 2 13486911 3 12700778 0

User · Answer

If you have Guava on your classpath  the following is a pretty readable alternative  Guava even has a fairly sensible custom List implementation for this case  so this shouldn t be inefficient   for char c   Lists charactersOf yourString            Do whatever you want          UPDATE  As  Alex noted  with Java 8 there s also CharSequence chars to use  Even the type is IntStream  so it can be mapped to chars like   yourString chars            mapToObj c - gt  Character valueOf  char  c            forEach c - gt  System out println c       Or whatever you want

User · Answer

StringTokenizer is totally unsuited to the task of breaking a string into its individual characters   With String split   you can do that easily by using a regex that matches nothing  e g    String   theChars   str split         But StringTokenizer doesn t use regexes  and there s no delimiter string you can specify that will match the nothing between characters   There is one cute little hack you can use to accomplish the same thing  use the string itself as the delimiter string  making every character in it a delimiter  and have it return the delimiters   StringTokenizer st   new StringTokenizer str  str  true     However  I only mention these options for the purpose of dismissing them   Both techniques break the original string into one-character strings instead of char primitives  and both involve a great deal of overhead in the form of object creation and string manipulation   Compare that to calling charAt   in a for loop  which incurs virtually no overhead

User · Answer

Two options  for int i   0  n   s length     i  lt  n   i           char c   s charAt i        or  for char c   s toCharArray             process c     The first is probably faster  then 2nd is probably more readable

User · Answer

See The Java Tutorials  Strings   public class StringDemo       public static void main String   args            String palindrome    Dot saw I was Tod           int len   palindrome length            char   tempCharArray   new char len           char   charArray   new char len               put original string in an array of chars         for  int i   0  i  lt  len  i                  tempCharArray i    palindrome charAt i                          reverse array of chars         for  int j   0  j  lt  len  j                  charArray j    tempCharArray len - 1 - j                      String reversePalindrome    new String charArray           System out println reversePalindrome             Put the length into int len and use for loop

User · Answer

I use a for loop to iterate the string and use charAt   to get each character to examine it   Since the String is implemented with an array  the charAt   method is a constant time operation   String s       stuff       for  int i   0  i  lt  s length    i         char c   s charAt i                 Process char     That s what I would do   It seems the easiest to me   As far as correctness goes  I don t believe that exists here   It is all based on your personal style

User · Answer

Note most of the other techniques described here break down if you re dealing with characters outside of the BMP  Unicode Basic Multilingual Plane   i e  code points that are outside of the u0000-uFFFF range  This will only happen rarely  since the code points outside this are mostly assigned to dead languages  But there are some useful characters outside this  for example some code points used for mathematical notation  and some used to encode proper names in Chinese   In that case your code will be   String str           int offset   0  strLen   str length    while  offset  lt  strLen      int curChar   str codePointAt offset     offset    Character charCount curChar        do something with curChar     The Character charCount int  method requires Java 5    Source  http   mindprod com jgloss codepoint html

User · Answer

There are some dedicated classes for this   import java text     final CharacterIterator it   new StringCharacterIterator s   for char c   it first    c    CharacterIterator DONE  c   it next            process c

User · Answer

There are some dedicated classes for this   import java text     final CharacterIterator it   new StringCharacterIterator s   for char c   it first    c    CharacterIterator DONE  c   it next            process c

User · Answer

I wouldn t use StringTokenizer as it is one of classes in the JDK that s legacy   The javadoc says      StringTokenizer is a legacy class that   is retained for compatibility reasons   although its use is discouraged in new   code  It is recommended that anyone   seeking this functionality use the   split  method of String or the   java util regex package instead

User · Answer

I use a for loop to iterate the string and use charAt   to get each character to examine it   Since the String is implemented with an array  the charAt   method is a constant time operation   String s       stuff       for  int i   0  i  lt  s length    i         char c   s charAt i                 Process char     That s what I would do   It seems the easiest to me   As far as correctness goes  I don t believe that exists here   It is all based on your personal style

[java] What is the easiest/best/most correct way to iterate through the characters of a string in Java?

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