Java by API/java.util/IdentityHashMap

new IdentityHashMap()

 
import java.util.IdentityHashMap;
import java.util.Map;
public class Main {
  public static void main(String[] argv) throws Exception {
    Map<Object, Object> objMap = new IdentityHashMap<Object, Object>();
    Object o1 = new Integer(123);
    Object o2 = new Integer(123);
    objMap.put(o1, "first");
    objMap.put(o2, "second");
    Object v1 = objMap.get(o1); // first
    Object v2 = objMap.get(o2); // second
  }
}