Unit 1.7 – Hacks (Answers)

Popcorn Hack #1: Using Documentation

import java.util.ArrayList;

public class PopcornHack1 {
    public static void main(String[] args) {
        // 1) 3^4 using Math.pow
        double threePowFour = Math.pow(3, 4);
        System.out.println("3^4 = " + threePowFour);

        // 2) sqrt(64) using Math.sqrt
        double sqrt64 = Math.sqrt(64);
        System.out.println("sqrt(64) = " + sqrt64);

        // 3) Create ArrayList of Strings
        ArrayList<String> colors = new ArrayList<>();

        // 4) Add 3 colors
        colors.add("red");
        colors.add("blue");
        colors.add("green");

        // 5) Print the size
        System.out.println("colors size = " + colors.size());

        // Optional: quick sanity print
        System.out.println("colors = " + colors);
    }
}

Popcorn Hack 2: Attributes and Behaviors


```python
public class Book {
    //Attributes
    private String title;
    private String author;
    private int pages;

    // Constructor
    public Book(String title, String author, int pages) {
        this.title = title;
        this.author = author;
        this.pages = pages;
    }

    // displayInfo(): print all book info
    public void displayInfo() {
        System.out.println("Title: " + title);
        System.out.println("Author: " + author);
        System.out.println("Pages: " + pages);
    }

    // isLong(): return true if pages > 300
    public boolean isLong() {
        return pages > 300;
    }

    // Simple test runner
    public static void main(String[] args) {
        Book myBook = new Book("Java Basics", "John Doe", 350);
        myBook.displayInfo();
        System.out.println("isLong = " + myBook.isLong());
    }
}

Expected Output:

3^4 = 81.0 sqrt(64) = 8.0 colors size = 3 colors = [red, blue, green]

Expected Output:

Title: Java Basics Author: John Doe Pages: 350 isLong = true

// Phone.java
import java.util.ArrayList;

public class Phone {
    // Attributes (4)
    private String brand;
    private String model;
    private int batteryLevel;
    private ArrayList<String> contacts;
    
    // Constructor - sets brand and model, initializes empty contacts list
    public Phone(String brand, String model) {
        this.brand = brand;
        this.model = model;
        this.batteryLevel = 100;
        this.contacts = new ArrayList<String>();
    }
    
    // displayInfo() - prints brand, model, and battery level
    public void displayInfo() {
        System.out.println("Brand: " + brand);
        System.out.println("Model: " + model);
        System.out.println("Battery Level: " + batteryLevel + "%");
    }
    
    // addContact(String name) - adds name to contacts list
    public void addContact(String name) {
        contacts.add(name);
        System.out.println("Contact '" + name + "' added successfully!");
    }
    
    // showContacts() - prints all contacts
    public void showContacts() {
        System.out.println("\nContacts List:");
        if (contacts.isEmpty()) {
            System.out.println("No contacts available.");
        } else {
            for (int i = 0; i < contacts.size(); i++) {
                System.out.println((i + 1) + ". " + contacts.get(i));
            }
        }
    }
    
    // usePhone(int minutes) - decreases battery by minutes used
    public void usePhone(int minutes) {
        batteryLevel -= minutes;
        if (batteryLevel < 0) {
            batteryLevel = 0;
        }
        System.out.println("Used phone for " + minutes + " minutes. Battery remaining: " + batteryLevel + "%");
    }
}

// PhoneTest.java
public class PhoneTest {
    public static void main(String[] args) {
        // Create 2 Phone objects
        Phone phone1 = new Phone("Apple", "iPhone 15");
        Phone phone2 = new Phone("Samsung", "Galaxy S24");
        
        System.out.println("=== PHONE 1 ===");
        // Add 3 contacts to phone1
        phone1.addContact("Alice Johnson");
        phone1.addContact("Bob Smith");
        phone1.addContact("Charlie Brown");
        
        // Use phone1 for some minutes
        phone1.usePhone(25);
        
        // Display phone1 information
        System.out.println("\n--- Phone 1 Information ---");
        phone1.displayInfo();
        phone1.showContacts();
        
        System.out.println("\n\n=== PHONE 2 ===");
        // Add 3 contacts to phone2
        phone2.addContact("David Lee");
        phone2.addContact("Emma Watson");
        phone2.addContact("Frank Miller");
        
        // Use phone2 for some minutes
        phone2.usePhone(40);
        
        // Display phone2 information
        System.out.println("\n--- Phone 2 Information ---");
        phone2.displayInfo();
        phone2.showContacts();
    }
}

output

=== PHONE 1 === Contact ‘Alice Johnson’ added successfully! Contact ‘Bob Smith’ added successfully! Contact ‘Charlie Brown’ added successfully! Used phone for 25 minutes. Battery remaining: 75%

— Phone 1 Information — Brand: Apple Model: iPhone 15 Battery Level: 75%

Contacts List:

Alice Johnson
Bob Smith
Charlie Brown

=== PHONE 2 === Contact ‘David Lee’ added successfully! Contact ‘Emma Watson’ added successfully! Contact ‘Frank Miller’ added successfully! Used phone for 40 minutes. Battery remaining: 60%

— Phone 2 Information — Brand: Samsung Model: Galaxy S24 Battery Level: 60%

Contacts List:

David Lee
Emma Watson
Frank Miller