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dependency_inversion.java
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dependency_inversion.java
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// Bad example
public class LightBulb {
public void turnOn() {
System.out.println("LightBulb: Bulb turned on...");
}
public void turnOff() {
System.out.println("LightBulb: Bulb turned off...");
}
}
public class ElectricPowerSwitch {
public LightBulb lightBulb;
public boolean on;
public ElectricPowerSwitch(LightBulb lightBulb) {
this.lightBulb = lightBulb;
this.on = false;
}
public boolean isOn() {
return this.on;
}
public void press(){
boolean checkOn = isOn();
if (checkOn) {
lightBulb.turnOff();
this.on = false;
} else {
lightBulb.turnOn();
this.on = true;
}
}
}
/* Our switch is now ready for use to turn on and off the light bulb. But the
mistake we did is apparent. Our high-level ElectricPowerSwitch class is directly
dependent on the low-level LightBulb class. if you see in the code, the
LightBulb class is hardcoded in ElectricPowerSwitch. But, a switch should not
be tied to a bulb. It should be able to turn on and off other appliances and
devices too, say a fan, an AC, or the entire lightning system of an amusement
park. Now, imagine the modifications we will require in the ElectricPowerSwitch
class each time we add a new appliance or device. */
// THE SOLUTION
public interface Switch {
boolean isOn();
void press();
}
public interface Switchable {
void turnOn();
void turnOff();
}
public class ElectricPowerSwitch implements Switch {
public Switchable client;
public boolean on;
public ElectricPowerSwitch(Switchable client) {
this.client = client;
this.on = false;
}
public boolean isOn() {
return this.on;
}
public void press(){
boolean checkOn = isOn();
if (checkOn) {
client.turnOff();
this.on = false;
} else {
client.turnOn();
this.on = true;
}
}
}
public class LightBulb implements Switchable {
@Override
public void turnOn() {
System.out.println("LightBulb: Bulb turned on...");
}
@Override
public void turnOff() {
System.out.println("LightBulb: Bulb turned off...");
}
}
public class Fan implements Switchable {
@Override
public void turnOn() {
System.out.println("Fan: Fan turned on...");
}
@Override
public void turnOff() {
System.out.println("Fan: Fan turned off...");
}
}