You can also think of it this way. If you remove the diode from the circuit, you will have two terminals, A and B (across the 2.2K resistor). The voltage that the diode or any component will see when connected to these terminals will be the voltage drop across the 2.2K resistor. You can find the voltage drop across that resistor by using the voltage divider formula. And from here, you can go ahead to find the current.