How can I initialise a static Map?

Question

How would you initialise a static Map in Java?

Method one: static initialiser
Method two: instance initialiser (anonymous subclass) or some other m

Answer 1

With Eclipse Collections, all of the following will work:

import java.util.Map;

import org.eclipse.collections.api.map.ImmutableMap;
import org.eclipse.collections.api.map.MutableMap;
import org.eclipse.collections.impl.factory.Maps;

public class StaticMapsTest
{
    private static final Map MAP =
        Maps.mutable.with(1, "one", 2, "two");

    private static final MutableMap MUTABLE_MAP =
       Maps.mutable.with(1, "one", 2, "two");


    private static final MutableMap UNMODIFIABLE_MAP =
        Maps.mutable.with(1, "one", 2, "two").asUnmodifiable();


    private static final MutableMap SYNCHRONIZED_MAP =
        Maps.mutable.with(1, "one", 2, "two").asSynchronized();


    private static final ImmutableMap IMMUTABLE_MAP =
        Maps.mutable.with(1, "one", 2, "two").toImmutable();


    private static final ImmutableMap IMMUTABLE_MAP2 =
        Maps.immutable.with(1, "one", 2, "two");
}

You can also statically initialize primitive maps with Eclipse Collections.

import org.eclipse.collections.api.map.primitive.ImmutableIntObjectMap;
import org.eclipse.collections.api.map.primitive.MutableIntObjectMap;
import org.eclipse.collections.impl.factory.primitive.IntObjectMaps;

public class StaticPrimitiveMapsTest
{
    private static final MutableIntObjectMap MUTABLE_INT_OBJ_MAP =
            IntObjectMaps.mutable.empty()
                    .withKeyValue(1, "one")
                    .withKeyValue(2, "two");

    private static final MutableIntObjectMap UNMODIFIABLE_INT_OBJ_MAP =
            IntObjectMaps.mutable.empty()
                    .withKeyValue(1, "one")
                    .withKeyValue(2, "two")
                    .asUnmodifiable();

    private static final MutableIntObjectMap SYNCHRONIZED_INT_OBJ_MAP =
            IntObjectMaps.mutable.empty()
                    .withKeyValue(1, "one")
                    .withKeyValue(2, "two")
                    .asSynchronized();

    private static final ImmutableIntObjectMap IMMUTABLE_INT_OBJ_MAP =
            IntObjectMaps.mutable.empty()
                    .withKeyValue(1, "one")
                    .withKeyValue(2, "two")
                    .toImmutable();

    private static final ImmutableIntObjectMap IMMUTABLE_INT_OBJ_MAP2 =
            IntObjectMaps.immutable.empty()
                    .newWithKeyValue(1, "one")
                    .newWithKeyValue(2, "two");
} 

Note: I am a committer for Eclipse Collections