Quiz J3-1

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Question 1

Consider the classes below:

interface WallOutlet {
    // Frequency is different from country to country
    public double getFrequency();

    public double getPower();
}

interface Battery {
    public double getSize();

    public double getPower();
}

class Electricity implements Battery {
    public int amp_hours =0;
    public boolean alternating_current=false;
    public double voltage =0.0;

    public double getSize() {
        return amp_hours;
    }

    public double getPower() {
        return amp_hours * voltage;
    }
}

class PowerPlant extends Electricity implements WallOutlet {
    public PowerPlant() {
        super();
        this.amp_hours = 100;
        this.alternating_current = true;
        this.voltage = 120.0;
    }

    public double getFrequency() {
        return 240;
    }

    public double getPower() {
        //Half since it's AC
        return super.getPower() /2;
    }
}

Someone who works at the Seabrook Station Nuclear Plant decided they want to use
it as a battery to charge their phone! What’s the output of the program below?

public class Main {
    public static void main(final String args[]) {
        PowerPlant seabrook_station = new PowerPlant();
        System.out.println("Power level: "+((Battery)seabrook_station).getPower());
    }
}

Question 2

Say we add the class below to our power program:

class AABattery extends Electricity implements Battery{
    public double getPower() {
        // AA Batteries are weak :/
        return 1.0;
    }

    public double getSize() {
        return super.getSize();
    }
}

Now in the program below someone tries to convert a AA battery to a power plant,
what’s the output?

    public static void main(final String args[]) {
        AABattery remote_battery = new AABattery();
        PowerPlant personal_power_plant = (PowerPlant)((Battery) remote_battery);
        System.out.println("Power level: "+personal_power_plant.getFrequency());
    }

Question 3

What if someone does the opposite, and tries to turn a Power Plant into a AA
battery?

    public static void main(final String args[]) {
        PowerPlant power_plant = new PowerPlant();
        AABattery personal_power_plant = (AABattery)((Battery) power_plant);
        System.out.println("Power level: "+personal_power_plant.getPower());
    }

Question 4

Finally someone added a converter from AA Batteries to Power Plants. What’s the output of the below program?

    public static PowerPlant powerPlantCreator(Electricity e){
        if(e instanceof PowerPlant)
            return (PowerPlant)e;
        else if(e instanceof AABattery){
            PowerPlant p = new PowerPlant();
            p.alternating_current = true;
            p.amp_hours = e.amp_hours;
            // Power plants output way higher voltages
            p.voltage = e.voltage * 100;
            return p;
        }
        return null;
    }
    public static void main(final String args[]) {
        AABattery remote_battery = new AABattery();
        PowerPlant personal_power_plant = powerPlantCreator(remote_battery);
        System.out.println("Power level: "+personal_power_plant.getPower());
    }