Java OOP

SHORT ANSWER QUESTIONS

INSTANCE METHODS

QUESTIONS

Fill the blanks and short answer questions. Solutions are at the bottom of this document.

a) The three main components of classes are __________, __________ and ___________.

b) What is the difference between instance methods and static methods in terms of the method header (method prototype)?

c) What is the difference between instance methods and static methods in terms of calling the method?

d) What is the difference between instance methods and static methods in terms of the data (variables) they have access to?

e) Consider the class below. Write the line of code that will create an instance of type Thing named ted.

public class Thing

{

public String stuff;

public int amount;

}

f) Consider the Thing class above. Write the instance method thatsOdd() that will output the content of stuff if the value of amount is an even number. However, when amount is an odd number, the method should output “That’s odd”.

g) Call the thatsOdd() method from the previous question on the Thing object named ted.

h) The class below allows one to create objects that represent squares. Add the instance method named area() that returns the area of the square.

public class Square

{

public double sideLength;

public Square(double tsl)

{

sideLength = tsl;

}

}

i) Consider the Vote class below. It allows you to create a Vote object that holds two voting options. Over the next few questions, you will add functionality to make it track votes for the different options.

First, how many instance variables, instance methods and constructors does it have?

public class Vote

{

public String option1;

public String option2;

public int count1;

public int count2;

public Vote(String op1, String op2)

{

option1 = op1;

option2 = op2;

count1 = 0;

count2 = 0;

}

}

j) Using the Vote class from above, create a Vote object with the options “Donald Trump” and “Joe Biden”. You can also use other options if you prefer.

k) Inside the class Vote, write the instance method called outputOptions that will demonstrate the voting options. The outputted statements should look like:

Your voting options:
Option 1: Donald Trump
Option 2: Joe Biden

Of course, the options displayed need to match the options in the instance variables.

l) Inside the class Vote from above, add the instance method named voteFor(int op) that will get a value of 1 or 2. The method then increases the count for the corresponding option.

m) Again inside the Vote class, add a results method that will output the current results of the vote. It should look something like this:

Vote results:
Donald Trump: 54 votes
Joe Biden: 55 votes

n) Still inside the Vote class, add a winner method that will return the winner based on the current results. The method can return either option1, option2 or the word “tie” in the case that the result is a tie.

Note that this method is different than the other methods as it doesn’t output the winner, but rather it returns it.

SOLUTIONS

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