Session 4

TicketMachine.java

/**
 * A TicketMachine that sells tickets for a fixed price.
 * Demonstrates Javadoc comments with preconditions and postconditions.
 * 
 * @author An AP Java student
 * @version 1.0
 * @since 2025
 */
public class TicketMachine {
    private int price;     // price of a single ticket
    private int balance;   // money inserted by the user
    private int total;     // total money collected by the machine

    /**
     * Constructs a TicketMachine with the given ticket price.
     *
     * @param ticketPrice the price of a single ticket
     * Precondition: ticketPrice > 0
     * Postcondition: price is set to ticketPrice, balance and total are 0
     */
    public TicketMachine(int ticketPrice) {
        price = ticketPrice;
        balance = 0;
        total = 0;
    }

    /**
     * Inserts money into the machine.
     *
     * @param amount the amount of money to insert
     * Precondition: amount > 0
     * Postcondition: balance is increased by amount
     */
    public void insertMoney(int amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    /**
     * Prints a ticket if enough money has been inserted.
     *
     * Precondition: balance >= price
     * Postcondition: balance is decreased by price, 
     *                total is increased by price
     */
    public void printTicket() {
        if (balance >= price) {
            // simulate ticket printing
            System.out.println("##################");
            System.out.println("# Ticket");
            System.out.println("# Price: " + price + " cents");
            System.out.println("##################");
            System.out.println();

            balance -= price;
            total += price;
        } else {
            System.out.println("You must insert at least: " 
                + (price - balance) + " more cents.");
        }
    }

    /**
     * Returns the current balance (unspent money).
     *
     * @return the current balance
     * Precondition: none
     * Postcondition: balance remains unchanged
     */
    public int getBalance() {
        return balance;
    }

    /**
     * Empties the machine of all collected money.
     *
     * @return the total money collected
     * Precondition: none
     * Postcondition: total is reset to 0
     */
    public int emptyMachine() {
        int amount = total;
        total = 0;
        return amount;
    }
}

GamePoints.java

public class GamePoints {
    public static void main(String[] args) {
        int level1Points = 120;
        int level2Points = 45;

        int totalPoints = level1Points + level2Points;
        int pointDifference = level1Points - level2Points;
        int bonusMultiplier = level1Points * 2;
        int averagePoints = totalPoints / 2;
        int remainderPoints = totalPoints % 2;

        System.out.println(totalPoints);
        System.out.println(pointDifference);
        System.out.println(bonusMultiplier);
        System.out.println(averagePoints);
        System.out.println(remainderPoints);
    }
}

OldMacDonaldv1.java

public class OldMacDonaldv1 {
    public static void main(String args[]) {
        System.out.println("Old MacDonald had a farm.");
        System.out.println("E-I-E-I-O");
        System.out.println("And on this farm, they had a cow.");
        System.out.println("E-I-E-I-O");
        System.out.println("With a moo moo here and a moo moo there");
        System.out.println("Here a moo, there a moo, everywhere a moo moo");
        System.out.println("Old MacDonald had a farm");
        System.out.println("E-I-E-I-O");
    }
}

OldMacDonaldv2.java

public class OldMacDonaldv2 {
    public static void intro() {
        System.out.println("Old MacDonald had a farm");
        chorus();
    }

    public static void chorus() {
        System.out.println("E-I-E-I-O");
    }

    public static void main(String[] args) {
        intro();
        System.out.println("And on that farm they had a cow.");
        chorus();
        System.out.println("With a moo moo here and a moo moo there");
        System.out.println("Here a moo, there a moo, everywhere a moo moo");

        // TODO:
        // 1. Call the method intro()

        // 2. Print out the line "And on that farm..."
        //    with a duck or another animal

        // 3. Call the method chorus

        // 4. Print out the lines with the appropriate animal sounds

        // 5. Call the method intro again

    }
}

OldMacDonaldv3.java

public class OldMacDonaldv3 {
    public static void main(String args[]) {
        System.out.println("Old MacDonald had a farm.");
        System.out.println("E-I-E-I-O");
        System.out.println("And on this farm, they had a cow.");
        System.out.println("E-I-E-I-O");
        System.out.println("With a moo moo here and a moo moo there");
        System.out.println("Here a moo, there a moo, everywhere a moo moo");
        System.out.println("Old MacDonald had a farm");
        System.out.println("E-I-E-I-O");
        System.out.println("And on this farm, they had a duck.");
        System.out.println("E-I-E-I-O");
        System.out.println("With a quack quack here and a quack quack there");
        System.out.println("Here a quack, there a quack, everywhere a quack quack");
        System.out.println("Old MacDonald had a farm");
        System.out.println("E-I-E-I-O");
    }
}

OldMacDonaldv4.java

public class OldMacDonaldv4 {
    public static void main(String args[]) {
        intro();
        verse("cow", "moo");
        intro();
        verse("duck", "quack");
        intro();
    }

    /**
     * The verse method prints out a verse for any given animal and sound.
     *
     * @param animal the name of the animal
     * @param sound  the sound the animal makes
     */
    public static void verse(String animal, String sound) {
        System.out.println("And on this farm, they had a " + animal);
        chorus();
        System.out.println("With a " + sound + " " + sound
                + " here and a " + sound + " " + sound + " there");
        System.out.println("Here a " + sound
                + ", there a " + sound
                + ", everywhere a " + sound + " " + sound);
    }

    /**
     * The intro method prints the introductory line of the song
     * and then calls the chorus method.
     */
    public static void intro() {
        System.out.println("Old MacDonald had a farm");
        chorus();
    }

    /**
     * The chorus method prints the repeating "E-I-E-I-O" line.
     */
    public static void chorus() {
        System.out.println("E-I-E-I-O");
    }
}

AntsSong.java

public class AntsSong
{
    public static void chorus(String num)
    {
        System.out.println("The ants go marching " + num
                         + " by " + num + " hurrah, hurrah");
        System.out.println("The ants go marching " + num
                         + " by " + num + " hurrah, hurrah");
    }

    public static void verse(String num, String action)
    {
        System.out.println("The ants go marching " + num + " by " + num);
        System.out.println("The little one stops to " + action);
        System.out.println("And they all go marching down to the ground");
        System.out.println("To get out of the rain, BOOM! BOOM! BOOM! BOOM!\n");
    }

    public static void main(String args[])
    {
        // Call the chorus and verse methods
        // with the correct arguments
        // to print out all three verses above.



    }
}

PoemLab.java

/**
 * The Poem class...
 * 
 * @author
 * @since
 * @version
 */
 
import java.util.*;

public class PoemLab {

    // prints a simple header
    public static void intro() {
        System.out.println("Stopping by Woods — A Programmed Poem");
        System.out.println("in the style of Robert Frost (1923)");
        System.out.println("--------------------------------------");
        System.out.println();
    }

    /**
     * Prints a 4-line stanza inspired by the poem's scene/thought pattern.
     * @param place a location detail (e.g., "the woods near the village")
     * @param time a time/mood detail (e.g., "this quiet winter evening")
     * @param image a sensory image (e.g., "the sweep of easy wind and downy flake")
     * @param innerThought a reflective line (e.g., "I watch the dark fill up the snow")
     */
    public static void stanza(String place, String time, String image, String innerThought) {
        System.out.println("Whose " + place + " these are, I think I know;");
        System.out.println("It is " + time + " and softly still.");
        System.out.println("I notice " + image + ", slow and low,");
        System.out.println(innerThought + ".");
        System.out.println();
    }

    // Refrain method: echo the poem’s famous closing repetition.
    public static void chorus() {
        System.out.println("And miles to go before I sleep,");
        System.out.println("And miles to go before I sleep.");
        System.out.println();
    }

    public static void main(String[] args) {
        // Initialize the Scanner. Declare a variable named in
        // that reads from System.in
        Scanner in = new Scanner(System.in);
        
        intro();

        // Example stanza calls (you must add/modify your own):
        stanza(
            "woods by the village road",
            "this hush of falling snow tonight",
            "the whispering wind and downy flakes",
            "I pause and let the quiet fill"
        );

        stanza(
            "quiet grove beyond the lake",
            "a late and silver-stitched twilight",
            "hoof-bells chiming once, then still",
            "I weigh the pull of rest against the path"
        );

        // TODO #1:
        // Write a THIRD stanza with your own vivid imagery.
        // Change all four parameters so the scene evolves.
        // stanza("<place>", "<time>", "<image>", "<innerThought>");

        // TODO #2 
        // Write a FOURTH stanza that adds a subtle shift in mood or choice.
        // stanza("<place>", "<time>", "<image>", "<innerThought>");

        // TODO #3:
        // After your FINAL stanza, call the chorus to close the poem:
        // chorus();
    }
}