How can I iterate through a string in Java?
I'm trying to use a foreach style for loop
for(char x : examplestring)
{
//action
}
views:
147answers:
4
+7
A:
Java Strings aren't cahracter Iterable. You'll need:
for (int i=0; i<examplestring.length(); i++) {
char c = examplestring.charAt(i);
...
}
Awkward I know.
cletus
2010-09-26 18:11:36
Alright thanks, yeah I thought it'd be easier.
rar
2010-09-26 18:13:52
+7
A:
If you want to use enhanced loop, you can convert the string to charArray
for (char ch : exampleString.toCharArray()){
System.out.println(ch);
}
surajz
2010-09-26 18:13:55
This is a lot worse that my version as it copies the `String` to a temporary array that is returned by the function.
cletus
2010-09-26 18:25:16
@cletus - you can't access original array - String is immutable so same should be the source array. But in Java you can always modify an array, which would cause to break Java optimizations (internig). Anyway one copy is faster than many `length()` and `charAt()`.
gertas
2010-09-26 18:43:23
@gertas that's exactly what I was saying. Because arrays are mutable it must be defensively copied. So you have the cost of that copy for what? Syntactic sugar. That's why this is a bad idea.
cletus
2010-09-26 18:48:36
@cletus: but here it isn't syntactic sugar. Generally we have rather memory vs cpu problem. I wouldn't mind if JVM optimizes access to String methods somehow, but still you call `.lenght()` and `.charAt()` for each char.
gertas
2010-09-26 18:56:40
@gertas: You need to give more credit to Java's optimizing compiler. Iterating by index is 2% faster on my machine (jre7-32bit-single) than iterating through a `char[]` copy.
Gunslinger47
2010-09-26 19:54:05
Like most things in java it won't be the CPU hit that kills you, it'll be all the garbage (temporary objects) you create. ‘length()‘ and ‘charAt()‘ are simple wrappers as well. If I found this code in a review I'd get it fixed.
cletus
2010-09-27 01:16:22
@cletus: [Escape analysis](http://java.dzone.com/articles/escape-analysis-java-6-update) should lessen that burden.
Gunslinger47
2010-09-27 06:48:57
+1
A:
Using Guava (r07) you can do this:
for(char c : Lists.charactersOf(someString)) { ... }
This has the convenience of using foreach while not copying the string to a new array. Lists.charactersOf returns a view of the string as a List.
ColinD
2010-09-26 19:03:28
+1. I didn't know that r07 was out. Though, interestingly, this is the slowest of the available options. It took 49% longer to complete than an equivillant `charAt` test.
Gunslinger47
2010-09-26 20:26:01
@Gunslinger47: I imagine the need to box and unbox each char for this would slow it down a bit. The method is probably more intended to adapt strings for use with various `Collection`-based APIs than just for iteration like this.
ColinD
2010-09-27 00:47:04
A:
How about this
for (int i=0;i < str.length;i++)
{
System.out.println(str.substring(i,i));
}
Suresh S
2010-09-28 08:14:48