Well. I found the answer myself. I am putting it here for the benefit of others.

State - districts is a 1-many relation (bi-directional relation).

here In Oops it becomes has a relations. So we have to design a state class which will contain a collection of ditricts as one of the attributes.

This is a bi-directional relation. So we have to design a distric class where a state class is denoted by means of an attribute.

State class will have getDistricts, setDistricts, addDistrict, deleteDistrict methods

District class will have getState, setState method

Alternatively, what can also be done is create a connection class

class connection {

Vector leftNodes;

Vector rightNodes;

}

here leftNode will contain a state and rightNode will contain multiple districts. THis design support many-to-Many, oneto-one and many-to-one and one to many relationships