Single Argument Method Implementation. 

class MyService extends AnExampleServiceGrpc.AnExampleServiceImplBase {
    @Override public void OneToOne (
        AnExampleRequest request,
        io.grpc.stub.StreamObserver<AnExampleResponse> responseObserver) {

        // Method implementation goes here ...

        responseObserver.onNext (response);
        responseObserver.onCompleted ();
    }
    ...
}

Server Initialization. 

io.grpc.Server server = io.grpc.ServerBuilder
    .forPort (8888).addService (new MyService ()).build ().start ();

server.awaitTermination ();