android/guava/src/com/google/common/collect/ImmutableBiMap.java
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
    checkEntryNotNull(k1, v1);
    checkEntryNotNull(k2, v2);
    return new RegularImmutableBiMap<K, V>(new Object[] {k1, v1, k2, v2}, 2);
  }
public static <K, V> ImmutableBiMap<K, V> of(K k1, V v1, K k2, V v2) {
    checkEntryNotNull(k1, v1);
    checkEntryNotNull(k2, v2);
    return new RegularImmutableBiMap<K, V>(new Object[] {k1, v1, k2, v2}, 2);
  }
Returns an immutable map containing the given entries, in order.

@throws IllegalArgumentException if duplicate keys or values are added