How do I access individual values within a string array within a Hashmap?

Question

My declaration of the map is as follows:

Map<Integer, String[]> mapVar = new HashMap<Integer, String[]>();

And I initialized it by making several string arrays and putting them into my map with a corresponding Integer.

I would like to then Iterate through all of the elements in my String array within the map. I tried these two possiblities but they're not giving me the right values:

for(int ii =0; ii < 2; ii++)
  System.out.println(((HashMap<Integer, String[]>)mapVar).values().toArray()[ii].toString());

and

mapVar.values().toString();

I also know the array and Integer are going into the map fine, I just don't know how to access them.

Thanks

The strings "13", "26" and "14", "28" I get [Ljava.lang.String;@342798e7 and [Ljava.lang.String;@13a78071 — Grammin
– Grammin, Commented May 20, 2011 at 15:02
That's the default toString() representation of a String[]. You want to print the individual Strings, not the array object's toString(). See my answer. — Isaac Truett
– Isaac Truett, Commented May 20, 2011 at 15:04
before you go all happy building a datastructure with hashmaps and arrays only, consider creating classes for the data you want to hold with appropriate implementations of hashCode and equals — Jochen Bedersdorfer
– Jochen Bedersdorfer, Commented May 20, 2011 at 16:29

Mikita Belahlazau · Accepted Answer · 2011-05-20 18:01:51Z

3

Try

for (String[] value : mapvar.values()) {
   System.out.println(Arrays.toString(value));
}

edited May 20, 2011 at 18:01

answered May 20, 2011 at 15:01

Mikita Belahlazau

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Isaac Truett · Accepted Answer · 2011-05-20 15:03:08Z

3

for (String[] strings : mapVar.values()) {
  for (String str : strings) {
     System.out.println(str);
  }
}

That will print all of the Strings in all of the arrays in the Map.

answered May 20, 2011 at 15:03

Isaac Truett

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pap · Accepted Answer · 2011-05-20 15:07:20Z

1

for (Map.Entry<Integer, String[]> entry : mapVar.entrySet()) {
   for (String s : entry.getValue()) {
      // do whatever
   }
}

answered May 20, 2011 at 15:07

pap

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ColinD · Accepted Answer · 2011-05-20 15:14:35Z

0

If you want to be able to access all the String values in the map as one unit rather than dealing with the intermediate arrays, I'd suggest using a Guava Multimap:

ListMultimap<Integer, String> multimap = ArrayListMultimap.create();
// put stuff in the multimap
for (String string : multimap.values()) { ... } // all strings in the multimap

Of course you can also access the list of Strings associated with a particular key:

List<String> valuesFor1 = multimap.get(1);

answered May 20, 2011 at 15:14

ColinD

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