How to initialize a public static final read-only LinkedMap (bidirectionnal map)

Question

I would like to create a

public static final LinkedMap myMap;

Somewhere I found something similar for Maps:

 public class Test {
        private static final Map<Integer, String> MY_MAP = createMap();

        private static Map<Integer, String> createMap() {
            Map<Integer, String> result = new HashMap<Integer, String>();
            result.put(1, "one");
            result.put(2, "two");
            return Collections.unmodifiableMap(result);
        }
    }

But I cannot apply the 'unmodifiableMap' method it to a LinkedMap. Can anybody help me? Is it possible at all?

Answer 1

The most popular workaround is almost certainly a Guava ImmutableMap. (Disclosure: I contribute to Guava.)

Map<Integer, String> map = ImmutableMap.of(
  1, "one",
  2, "two");

or

ImmutableMap<Integer, String> map = ImmutableMap
  .<Integer, String> builder()
  .put(1, "one")
  .put(2, "two")
  .build();

Without other libraries, the only workaround other than the one you've written is

static final Map<Integer, String> CONSTANT_MAP;
static {
  Map<Integer, String> tmp = new LinkedHashMap<Integer, String>();
  tmp.put(1, "one");
  tmp.put(2, "two");
  CONSTANT_MAP = Collections.unmodifiableMap(tmp);
}