java Converting a set to an array

Question

I'm trying to convert my set of Strings to an array of Strings so I can operate on them one by one. Is there a better way of doing this or is converting to arrays a good way? However, when I try converting to an array like below then I get errors as it doesn't think that it will always be strings passed in. Would appreciate some pointers.

Set<String> s;

s.add("a");
s.add("b");
String[] item =  s.toArray();

The reason you get errors is because `toArray` with no arguments returns an `Object[]`. You need to give it an argument, even a dummy argument like `new String[0]`, in order to get it to return an array of something else. See the javadoc [here](http://docs.oracle.com/javase/7/docs/api/java/util/Set.html#toArray(T[])). — ajb, Feb 08 '14 at 01:07

score 2 · Accepted Answer · answered Feb 08 '14 at 00:58

2

You do not have to convert a Set to an array just to operate on the elements. You can iterate over the elements directly

Set<String> s = new HashSet<>();
....
for (String item : s)
{
    do something...
}

answered Feb 08 '14 at 00:58

Jim Garrison

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score 1 · Answer 2 · answered Feb 08 '14 at 00:58

1

so I can operate on them one by one

You don't have to convert it to an array for that.

Instead iterate using the for-each loop or the iterator.

answered Feb 08 '14 at 00:58

Ajay George

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Maciej Cygan · Answer 3 · 2014-02-08T01:09:05.190

0

you can do something like this

String[] item = s.toArray(new String[s.size()]);

As per Java doc - toArray function ( which is the one you need )

toArray() Returns an array containing all of the elements in this list in proper sequence (from first to last element).

edited Feb 08 '14 at 01:09

answered Feb 08 '14 at 00:57

Maciej Cygan

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java Converting a set to an array

3 Answers3