Java: How to reparse 'Array.toString' again in Array?

Question

I have a array which I convert to string to use it as key in an hashmap. How is it possible to convert a string like this [5.0, -1.0, 2.0] again to an array consisting of three double values?

PS: I'm kind of new to java but I couldnt find a solution here or via google.

http://stackoverflow.com/a/3272808/86515 combined with Double.parseDouble — KitsuneYMG, Apr 29 '13 at 19:44
http://stackoverflow.com/questions/9101301/how-to-convert-string-array-to-double-array-in-one-line http://stackoverflow.com/questions/2454137/java-converting-string-in-array-to-double Try these. — j.jerrod.taylor, Apr 29 '13 at 19:46
Why not use a `List` as the key in the hash map, rather than a `String`? Trying to dump it into a `String` is definitely a code smell. — Louis Wasserman, Apr 29 '13 at 19:46
+1 for Louis' comment, but remember not to modify the list after you've started using it as a hash key. better yet, use an immutable list (like you'll find in the guava library) — Sean Patrick Floyd, Apr 29 '13 at 19:51

score 0 · Answer 1 · answered Apr 29 '13 at 19:44

0

There isn't any ready method for this. So, you have to create your own method, which will parse your string back into array of double-s. You can do it, using String.split(...) method for example.

answered Apr 29 '13 at 19:44

Andremoniy

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score 0 · Answer 2 · answered Apr 29 '13 at 19:44

0

See documentation for String.substring() and String.split().

answered Apr 29 '13 at 19:44

akostadinov

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score 0 · Answer 3 · answered Apr 29 '13 at 19:44

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Scanner sc = new Scanner(stringToParse);
ArrayList<Double> buffer = new ArrayList<>();
while(sc.hasNextDouble())
    buffer.add(sc.nextDouble());
Object[] doubles = buffer.toArray();

answered Apr 29 '13 at 19:44

gparyani

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the last line should be `Double[] doubles = buffer.toArray(new Double[buffer.size()])` – Sean Patrick Floyd Apr 29 '13 at 19:47
This answer returns a `Double[]`, OP was asking for a `double[]` – Óscar López Apr 29 '13 at 19:55

score 0 · Answer 4 · answered Apr 29 '13 at 19:45

0

Something like this might work

List<Double> yourDoubleList = new ArrayList<Double>();
String withoutBrackets = array.substring(1, array.length() - 1);
for(String number : withoutBrackets.split(",")) {
    yourDoubleList.add(Double.parseDouble(number));
}

answered Apr 29 '13 at 19:45

Petr Mensik

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This answer returns a `List`, OP was asking for a `double[]` – Óscar López Apr 29 '13 at 19:54
@ÓscarLópez yes, but arguably the list is still a better choice for usability (at least for a small number of doubles) – Sean Patrick Floyd Apr 29 '13 at 19:58

Óscar López · Accepted Answer · 2013-04-29T19:57:48.207

It's possible, with a bit of fiddling - and by the way, it's a very, very bad idea to use an array as a key to a Map (even if it's converted to a String), because it can change its contents. Try this:

String array = "[5.0, -1.0, 2.0]";
String[] data = array.substring(1, array.length()-1).split(", ");
double[] answer = new double[data.length];
for (int i = 0; i < data.length; i++)
    answer[i] = Double.parseDouble(data[i]);

Now answer will be an array of doubles with the values originally contained in the String.

Java: How to reparse 'Array.toString' again in Array?

5 Answers5