lab04

All of these questions deal with the ticket machine example bundled in this repo. You should fork this repo and clone the fork to work on the code locally.

How can we tell from just its header that setPrice is a method and not a constructor?

public void setPrice(int cost)

Complete the body of the setPrice method so that it assigns the value of its parameter to the price field. Write your new method in the lab04-ticket-machine.

Complete the body of the following method, whose purpose is to add the value of its parameter to a field named score.

/**
 * Increase score by the given number of points.
 */
public void increase(int points)
{
  ...
}

Is the increase method in the previous question a mutator? If so, how could you demonstrate this?

Complete the following method, whose purpose is to subtract the value of its parameter from a field named price. Add your new method to the lab04-ticket-machine.

/**
 * Reduce price by the given amount.
 */
public void discount(int amount)
{
  ...
}

Write down exactly what will be printed by the following statement:

System.out.println("My cat has green eyes.");

Add a method called prompt to the TicketMachine class in the lab04-ticket-machine. This should have a void return type and take no parameters. The body of the method should print the following single line of output:

Please insert the correct amount of money.

What do you think would be printed if you altered the fourth statement of printTicket so that price also has quotes around it, as follows?

System.out.println("# " + "price" + " cents.");

What would be printed here?

System.out.println("# price cents.");

Could either of the previous two versions be used to show the price of tickets in different ticket machines? Explain your answer.

Add a showPrice method to the TicketMachine class in the lab04-ticket-machine. This should have a void return type and take no parameters. The body of the method should print (here xyz should be replaced by the value held in the price field when the method is called):

The price of a ticket is xyz cents.

Create two ticket machines with differently priced tickets. Do calls to their showPrice methods show the same output, or different? How do you explain this effect?

Modify the constructor of TicketMachine in the lab04-ticket-machine so that it no longer has a parameter. Instead, the price of tickets should be fixed at 1,000 cents. What effect does this have when you construct ticket-machine objects within BlueJ?

Give the class two constructors. One should take a single parameter that specifies the price, and the other should take no parameter and set the price to be a default value of your choosing. Test your implementation by creating machines via the two different constructors.

Implement a method, empty, that simulates the effect of removing all money from the machine. This method should have a void return type, and its body should simply set the total field to zero. Does this method need to take any parameters? Test your method by creating a machine, inserting some money, printing some tickets, checking the total, and then emptying the machine. Is the empty method a mutator or an accessor?