Processing 1.0 - Processing Discourse - how to iterate over a string

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Index › Programming Questions & Help › Syntax Questions › how to iterate over a string

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how to iterate over a string (Read 1384 times)

mateooo Junior Member Offline Posts: 58	how to iterate over a string May 18^th, 2010, 5:39am hello how can i iterate over a string? im made a algorithms that create random strings like: jkasjdkslkdaslkdjlsjdlkasjdklsjdljsaldsjdlasdjlkasdjksald how can i iterate over the characters of a string? thanks

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: how to iterate over a string Reply #1 - May 18^th, 2010, 6:15am There are several ways... See String reference for some. What do you plan to do when iterating

martin_p

Re: how to iterate over a string
Reply #2 - May 18^th, 2010, 11:51am

You can even use the java character iterator (which you need to import or fully specify).

Code:


CharacterIterator it = new StringCharacterIterator(myString);
  for (char ch = it.first(); ch != CharacterIterator.DONE; ch = it.next()) {
....................}

It is not everyones taste owing to the syntax but I like it, as PhiLho says it really depends what you want to do.

Jo Wood Junior Member Offline Posts: 52	Re: how to iterate over a string Reply #3 - May 18^th, 2010, 12:16pm With the latest Java 5 syntax friendly version of Processing it can be simplified by using a 'for-each' loop: Quote: String myText = "This is a test"; for (char letter : myText.toCharArray()) { println(letter); }

martin_p Junior Member Offline Posts: 70 UK	Re: how to iterate over a string Reply #4 - May 19^th, 2010, 3:49am Hey that's really neat!

PhiLho YaBB Moderator Offline Posts: 4190 Near Paris (France)	Re: how to iterate over a string Reply #5 - May 19^th, 2010, 4:53am I was also thinking of the toCharArray(), indeed, which is practical but might be costly in memory for very large strings (as it duplicates the data). I admit I didn't know the CharacterIterator, probably rarely used, but better than using repeatedly substring() and avoiding the duplication to char array.

martin_p

Re: how to iterate over a string
Reply #6 - May 19^th, 2010, 6:07am

I'm not so keen about the toCharArray(), given the overhead pointed out by PhiLho (I've been working with some big lsystem Strings myself).

I just liked the syntactic sugar. Another thing about the CharacterIterator, is that If you want to use it with some new text, all you need to do is setText(newText) rather than create a new Iterator object, so I guess it is aimed at efficiency.

Jo Wood

Re: how to iterate over a string
Reply #7 - May 19^th, 2010, 6:27am

I guess it all comes down to the classic trade-off between storage efficiency and processing efficiency. I think strings would have to be pretty big (of order megabytes) for the storage efficiency to become an issue. If they were that big anyway, I'd be looking at exactly why I'd want to iterate over the string in the first place.

Personally, the main efficiency I look for in my code is clarity. Good clear code seems to save a lot of time and is less error prone. Other forms of optimisation come at the end, and only if really necessary. This is why I'm really happy that Processing now incorporates Java 5 syntax.

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