A Basic Object

In this section we$$ll build a small class together $($starting from the above template$),$ useful for managing a gift card balance. This class will keep track of the total balance and will allow for a starting total, deductions, and a balance report. To manage such details, we$$ll need a class$-$level $($or instance$)$ variable to store the balance, as well as a few methods to implement the actions mentioned above. Download GiftCard.java and look at the main method.

Explain to your partner what is happening in each line of the main method of GiftCard.$$ How do card$1,$ card$2,$ and card$3$ differ from each other, after each line of the code?$$

$($Tip: Just write a comment in your code for this.$)$

Add a class$-$level variable to track the balance at the top of the file. Should this variable be a char? A double?$$

$($Tip: A class$-$level variable is like a normal variable, but it is inside of a class and can only be accessed by accessing an instance of a class too. It's just like what you've already been doing since all Java programs are inside one big class, just make sure the variables are above your constructor.$)$

Add a constructor that will set the class$-$level instance variable you defined earlier when you create an instance of GiftCard. Check the main method for places where the GiftCard constructor is used, and make sure that constructor takes in the correct number of parameters.$$

$($Tip: remember, a constructor is for initializing vital variables of a class that may not always be the same value. In this case, the$$balance variable is the one we want to initialize $($because it might be different for each gift card$),$ and so our constructor should have one parameter. Inside of the constructor, you should set the$$balance$$variable to whatever the parameter value, or argument, is equal to$.)$

Add a void method setBalance$($double newBalance$)$ that resets the balance.$$

$($Tip: All this does is set the balance variable to a new value, whatever newBalance is equal to$.$ This is called a$$setter or$$mutator$$method$.)$

Make this function fail on negative input$$

$($Tip: if$-$statement inside of the setBalance method, before you actually set balance to be equal to newBalance$)$

Add a void method deduct$($double amount$)$ method that subtracts from the balance$$

$($Tip: This is another mutator method, but instead of completely replacing the old balance, you just do some simple subtraction. Keep in mind both of these methods will be before your$$main method.$)$

Make this function fail on a negative balance

Add a void method report$()$ that prints out the balance remaining on the gift card.$$

$($Tip: Print the value of balance to the console using$$System$.$out.print$().)$