Splitting words into letters in Java

Question

How can you split a word to its constituent letters?

Example of code which is not working

 class Test {
         public static void main( String[] args) {
             String[] result = "Stack Me 123 Heppa1 oeu".split("\\a");                                                                                   

             // output should be
             // S
             // t
             // a
             // c
             // k
             // M
             // e
             // H
             // e
             // ...
             for ( int x=0; x<result.length; x++) {
                 System.out.println(result[x] + "\n");
             }
         }
     }

The problem seems to be in the character \\a. It should be a [A-Za-z].

Your example doesn't make it clear if you want "123" to be split up or not. — patros, Oct 05 '09 at 19:29

score 56 · Accepted Answer · answered Oct 05 '09 at 19:28

56

You need to use split("");.

That will split it by every character.

However I think it would be better to iterate over a String's characters like so:

for (int i = 0;i < str.length(); i++){
    System.out.println(str.charAt(i));
}

It is unnecessary to create another copy of your String in a different form.

answered Oct 05 '09 at 19:28

jjnguy

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+1: Hmm, I didn't think about creating another copy of the string. Good point. – Powerlord Oct 05 '09 at 19:34
1

One thing to consider here is str.charAt(i) will return a char. So if you need a String you will need to do Character.toString(str.charAt(i)). This will create a copy of that character, but that is still better than O(n) space that using str.split("") would give you. – catalyst294 Feb 09 '14 at 16:51
1

this solution will give array of length 1 if input is empty string – rightful Jul 26 '20 at 19:53
The last comment is correct: An empty string is the **only** case where ```.split("")``` would add an extra (empty) element to the array. – Rautermann May 22 '21 at 21:30

score 30 · Answer 2 · answered Oct 05 '09 at 19:28

30

"Stack Me 123 Heppa1 oeu".toCharArray() ?

answered Oct 05 '09 at 19:28

Zed

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+1: Simple, concise, and can easily be fed to for. – Powerlord Oct 05 '09 at 19:33
1

Creating an extra char array is an extra step that is not necessary. – jjnguy Oct 05 '09 at 19:37
Depends. My _guess_ is that above a certain length an arrayCopy and direct array access is "faster" than calling hundreds of charAt's. – Zed Oct 05 '09 at 19:41
2

Calling `charAt` is O(1) because the String is implemented using an array in the back end. Creating a copy will be slower always. – jjnguy Oct 05 '09 at 19:46
1

Calling `charAt(i)` is implemented to first make a sanity check on the input parameter then offsetting it with the internal offset, and after this yes, it is an array access. – Zed Oct 05 '09 at 19:55

score 8 · Answer 3 · edited Dec 07 '15 at 16:23

8

You can use

String [] strArr = Str.split("");

edited Dec 07 '15 at 16:23

Tunaki

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answered Dec 07 '15 at 16:17

6

This adds an extra blank string to 0 position so array is one extra. – JPM May 23 '16 at 19:21

score 6 · Answer 4 · answered Oct 05 '09 at 19:45

Including numbers but not whitespace:

"Stack Me 123 Heppa1 oeu".replaceAll("\\W","").toCharArray();

=> S, t, a, c, k, M, e, 1, 2, 3, H, e, p, p, a, 1, o, e, u

Without numbers and whitespace:

"Stack Me 123 Heppa1 oeu".replaceAll("[^a-z^A-Z]","").toCharArray()

=> S, t, a, c, k, M, e, H, e, p, p, a, o, e, u

score 3 · Answer 5 · edited Oct 05 '09 at 19:30

3

 char[] result = "Stack Me 123 Heppa1 oeu".toCharArray();

edited Oct 05 '09 at 19:30

jjnguy

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answered Oct 05 '09 at 19:29

David

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score 2 · Answer 6 · answered Oct 05 '09 at 19:34

2

I'm pretty sure he doesn't want the spaces to be output though.

for (char c: s.toCharArray()) {
    if (isAlpha(c)) {
       System.out.println(c);
     }
}

answered Oct 05 '09 at 19:34

Gandalf

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score 0 · Answer 7 · edited Jul 01 '11 at 11:24

0

String[] result = "Stack Me 123 Heppa1 oeu".split("**(?<=\\G.{1})**");
System.out.println(java.util.Arrays.toString(result));

edited Jul 01 '11 at 11:24

idursun

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answered Jul 01 '11 at 10:19

shiva krishna komuravelly

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Your code thrown below error when executed. `Exception in thread "main" java.util.regex.PatternSyntaxException: Dangling meta character '*' near index 0 **(?<=\G.{1})** ^ at java.util.regex.Pattern.error(Pattern.java:1924) at java.util.regex.Pattern.sequence(Pattern.java:2090) at java.util.regex.Pattern.expr(Pattern.java:1964) at java.util.regex.Pattern.compile(Pattern.java:1665) at java.util.regex.Pattern.(Pattern.java:1337) at java.util.regex.Pattern.compile(Pattern.java:1022) at java.lang.String.split(String.java:2313) at java.lang.String.split(String.java:2355)` – Suresh Nov 03 '17 at 06:42

Splitting words into letters in Java

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