Communicator interface
package cv3;

public interface Communicator {
	public void send(Communicator com, String data);
	public void receive(String data);
	public void print_received();
}

Bluetooth
package cv3;

public class Bluetooth implements Communicator{
	private String buffer = "";

	@Override
	public void send(Communicator com, String data) {
		System.out.println("Sending data over Bluetooth");
		com.receive(data);
	}

	@Override
	public void receive(String data) {
		System.out.println("Receiving data over Bluetooth");
		buffer += data;
	}

	@Override
	public void print_received() {
		System.out.println("Received data:");
		System.out.println(buffer);
	}

}

Phone
package cv3;

public class Phone {
	Communicator bt = new Bluetooth();
	Communicator infra = new Infra();
}

infra
package cv3;

public class Infra implements Communicator{
	private String buffer = "";

	@Override
	public void send(Communicator com, String data) {
		System.out.println("Sending data over Infra");
		com.receive(data);
	}

	@Override
	public void receive(String data) {
		System.out.println("Receiving data over Infra");
		buffer += data;
	}

	@Override
	public void print_received() {
		System.out.println("Received data:");
		System.out.println(buffer);
	}

}

main
package cv3;

public class Main {

	public static void main(String[] args) {
		Phone tomas = new Phone();
		Phone lucka = new Phone();

		tomas.bt.send(lucka.bt, "Ahoj, pujdeme na kafe?");
		lucka.infra.send(tomas.infra, "Tak jo");

		lucka.bt.print_received();
		tomas.infra.print_received();
	}

}