Java

OOP GUIDE / WORK

LAMP CLASS SOLUTIONS

TASK – PART 1 – LAMP CLASS WITHOUT ENCAPSULATION

Solution:

public class Lamp

{

//INSTANCE VARIABLES (DATA FIELDS)

public boolean isOn;

public int onCounter;

//CONSTRUCTOR(S)

public Lamp()

{

isOn = false;

onCounter = 0;

}

//INSTANCE METHOD(S)

public String toString()

{

String part1;

if (isOn == true)

part1 = "The lamp is ON. ";

else

part1 = "The lamp is OFF. ";

String part2 = "It has been on " + onCounter + " times.";

return part1 + part2;

}

}

TASK – PART 2 – TESTING THE LAMP CLASS

Solution:

public class LampTester

{

public static void main(String[] args)

{

Lamp pixar = new Lamp();

System.out.println(pixar);

pixar.isOn = true;

pixar.onCounter++;

pixar.isOn = false;

pixar.isOn = true;

pixar.onCounter++;

pixar.isOn = true; //was already true, so no counter increase

//Note that this is tricky. We have to remember to

//increase onCounter when we set isOn to true (unless

//it was already true before). Yuck!

System.out.println(pixar);

//There must be a better way!!! Hint hint! :)

}

}

TASK – PART 3 – SETUP

No work to show

TASK – PART 4 – ENCAPSULATED LAMP CLASS

Solution for Lamp class:

public class Lamp

{

//INSTANCE VARIABLES (DATA FIELDS)

private boolean isOn;

private int onCounter;

//CONSTRUCTOR(S)

public Lamp()

{

isOn = false;

onCounter = 0;

}

//INSTANCE METHOD(S)

public String toString()

{

String part1;

if (isOn == true)

part1 = "The lamp is ON. ";

else

part1 = "The lamp is OFF. ";

String part2 = "It has been on " + onCounter + " times.";

return part1 + part2;

}

public void switchOn()

{

if (isOn == false)

{

isOn = true;

onCounter++;

}

}

public void switchOff()

{

isOn = false;

}

public boolean getIsOn()

{

return isOn;

}

public int getOnCounter()

{

return onCounter;

}

public String getState()

{

if (isOn == true)

return "ON";

else

return "OFF";

}

}

Solution for LampTester class:

public class LampTester

{

public static void main(String[] args)

{

Lamp pixar = new Lamp();

System.out.println(pixar);

pixar.switchOn();

pixar.switchOn(); //does nothing

pixar.switchOff();

pixar.switchOn();

System.out.println(pixar);

System.out.println(pixar.getIsOn());

System.out.println(pixar.getOnCounter());

System.out.println(pixar.getState());

}

}