Frank Changes

java-org/classes-and-objects/topic.jsh

@@ -5,130 +5,283 @@ import java.util.ArrayList;
 // Exercise 1: Basic Class Creation
 // Create a Person class with name and age fields
 class Person {
-    // Your fields here
+    String name;
+    int age;
 
-    // Your constructor here
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String introduce() {
+        return "Hello, I'm " + name + " and I'm " + age + " years old.";
 
-    // Your introduce() method here
+    }
 
 }
 
+
 // Exercise 2: Class with Methods
 // Create a BankAccount class with account operations
-class BankAccount {
-    // Your fields here
-
-    // Your constructor here
-
-    // Your deposit method here
-
-    // Your withdraw method here
-
-    // Your getBalance method here
+public class BankAccount {
+    String accountNumber;
+    double balance;
+
+    public BankAccount(String accountNumber) {
+        this.accountNumber = accountNumber;
+        this.balance = 0.0;
+    }
+
+    public double deposit(double amount) {
+        balance += amount;
+        return balance;
+    }
+
+    public double withdraw(double amount) {
+        if(amount > 0 && amount <= balance) {
+            balance -= amount;
+        }
+        return balance;
+    }
 
-    // Your getAccountInfo method here
+    public double getBalance() {
+        return balance;
 
+    }
+
+    public String getAccountInfo() {
+        return "accountNumber: " + accountNumber + ", Balance: $" + balance; 
+    }
+
+
 }
 
 // Exercise 3: Object Creation and Usage
 // Create and return a Person object
 public Person createPerson(String name, int age) {
-    // Your code here
+    Person person = new Person(name, age);
+    return person;
 
 }
 
 // Create and return a BankAccount object
 public BankAccount createBankAccount(String accountNumber) {
-    // Your code here
+    BankAccount account = new BankAccount(accountNumber);
+    return account;
 
 }
 
 // Demonstrate creating and using a Person object
 public void demonstratePersonUsage() {
-    // Your code here
+    Person person = createPerson("Alice", 30);
+    System.out.println(person.introduce()); // 
 
 }
 
 // Exercise 4: Working with Multiple Objects
 // Create a Car class
 class Car {
     // Your fields here
+    String brand;
+    String model;
+    int year;
 
     // Your constructor here
+    public Car(String brand, String model, int year) {
+        this.brand = brand;
+        this.model = model;
+        this.year = year;
+    }
 
     // Your getCarInfo method here
+    public String getCarInfo() {
+        return "Car: " + brand + " " + model + ", Year: " + year;
+    }
 
     // Your isClassic method here (car is classic if > 25 years old)
+    public boolean isClassic() {
+        int currentYear = 2025;
+        return (currentYear - year) > 25;
+
+    }
+
+    public int getCarYear() {
+        return year;
+    }
 
 }
 
 // Compare two cars and return which is older
 public Car compareCars(Car car1, Car car2) {
-    // Your code here
+    if (car1.getCarYear() < car2.getCarYear()) {
+        return car1;
+    } else if (car1.getCarYear() > car2.getCarYear()){
+        return car2;
+    }
+    return null;
 
 }
 
 // Exercise 5: Object State and Behavior
 // Create a Counter class that can increment/decrement
 class Counter {
-    // Your fields here
-
-    // Your constructor here
-
-    // Your increment method here
-
-    // Your decrement method here
-
-    // Your reset method here
-
-    // Your getCount method here
+    private int count;
+
+    public Counter() {
+        this.count = 0;
+    }
+
+    public int increment() {
+        count++;
+        return count;
+    }
+
+    public int decrement() {
+        if (count > 0) {
+            count--;
+        }
+        return count;
+    }
+
+    public int reset() {
+        count = 0;
+        return count;
+    }
+
+    public int getCount() {
+        return count;
+    }
 
 }
 
+// Demonstrate the Counter classpublic class HelloWorld {
+   // public static void main(String[] args)
+
 // Exercise 6: Class with Validation
 // Create a Student class with input validation
+System.out.println("Student System");
 class Student {
-    // Your fields here
-
-    // Your constructor with validation here
-
-    // Your isHonorStudent method here
 
+    String name;
+    int grade;
+    double gpa;
+
+    public Student(String name, int grade, double gpa) throws Exception {
+        if ( name == null || name.isEmpty()) {
+            throw new Exception("Name cannot be null or empty");
+        }   
+        this.name = name;
+
+        if (grade < 1 || grade > 12) {
+            throw new Exception("Grade must be between 1 and 12");
+        } 
+        this.grade = grade;
+
+        if (gpa < 0.0 || gpa > 4.0) {
+            throw new Exception("GPA must be between 0.0 and");
+        }
+        this.gpa = gpa;
+
+    }
+
+    public boolean isHonorStudent() {
+        return gpa >= 3.5;
+    }
+
     // Your getStudentInfo method here
+    public String getStudentInfo(){
+        return "Student:" + name + ", Grade: " + grade + ", GPA: " + gpa;
+    }
 
 }
 
 // Exercise 7: Object Interaction
 // Create a Book class
+System.out.println("Book System");
 class Book {
     // Your fields here
+    String title;
+    String author;
+    boolean isCheckedOut;
 
     // Your constructor here
+    public Book(String title, String author, boolean isCheckedOut) {
+        this.title = title;
+        this.author = author;
+        this.isCheckedOut = isCheckedOut;
+    }
 
     // Add any helpful methods here
+    public String getTitle() {
+        return title;
+    }
+
+    public String getAuthor() {
+        return author;
+    }
+
+    public boolean getIsCheckedOut() {
+        return isCheckedOut;
+    }
 
 }
 
 // Create a Library class that manages books
-class Library {
+System.out.println("Library System");
+public class Library {
     // Your fields here
+    ArrayList<Book> books;
 
     // Your constructor here
+    public Library() {
+        books = new ArrayList<Book>();
+    }
+
 
     // Your addBook method here
-
+    public void addBook(Book book) {
+        books.add(book);
+    }
+
     // Your checkOutBook method here
-
+    public String checkOutBook(String title) {
+        for (Book book : books) {
+            if (book.getTitle().equalsIgnoreCase(title) && !book.getIsCheckedOut()) {
+                book.isCheckedOut = true;
+                return "Checked out; " + title;
+            } else if (book.getTitle().equalsIgnoreCase(title) && book.getIsCheckedOut()) {
+                return "Book is already checked out: " + title;
+            }
+        }
+        return "Book not found: " + title;
+
+    }
+
     // Your returnBook method here
+    public String returnBook(String title) {
+        for (Book book : books) {
+            if (book.getTitle().equalsIgnoreCase(title) && book.getIsCheckedOut()) {
+                book.isCheckedOut = false;
+                return "Returned Book; " + title;
+            } else if (book.getTitle().equalsIgnoreCase(title) && !book.getIsCheckedOut()) {
+                return "Book is already in the library: " + title;
+            }
+        }
+        return "Book not found: " + title;
+    }
+
 
     // Your getAvailableBooks method here
+    public int getAvailableBooks() {
+        return books.size();
+    }
 
 }
 
 // Test your classes here - uncomment and modify as needed
-/*
+
 System.out.println("Testing Person class:");
-Person person1 = createPerson("Alice", 30);
+Person person1 = createPerson("Frank", 30);
 Person person2 = new Person("Bob", 25);
 System.out.println(person1.introduce());
 System.out.println(person2.introduce());
@@ -192,4 +345,4 @@ System.out.println("After checking out 1984: " + library.getAvailableBooks());
 
 library.returnBook("1984");
 System.out.println("After returning 1984: " + library.getAvailableBooks());
-*/
+

java-org/nested-objects/topic.jsh

@@ -12,6 +12,10 @@ class Address {
 
     public Address(String street, String city, String state, String zipCode) {
         // TODO: Initialize all fields
+        this.street = street;
+        this.city = city;
+        this.state = state;
+        this.zipCode = zipCode;
     }
 
     public String getFullAddress() {
@@ -428,7 +432,7 @@ class Customer {
 
     public double getTotalBalance() {
         // TODO: Sum balances of all accounts
-        return 0.0;
+        return 12223343450.0;
     }
 
     public String getAccountSummary() {

java-org/parameters-and-return-values/NOTES.md

@@ -15,7 +15,7 @@ A method's signature defines its interface:
 ```java
 public returnType methodName(parameterType1 param1, parameterType2 param2) {
     // Method body
-    return someValue;  // Must match returnType
+    return someValue;   
 }
 ```
 
@@ -36,6 +36,7 @@ public double calculateInterest(double principal, double rate, int years) {
 public void processNumbers(int count, double amount, boolean isActive) {
     // count, amount, isActive are copies of the original values
     // Modifying them here doesn't affect the original values
+
 }
 ```
 
@@ -52,6 +53,7 @@ public void processList(ArrayList<String> items) {
 public double findAverage(double[] numbers) {
     // numbers refers to the same array as the caller
     // You can modify array contents, but not the array reference itself
+    for ()
 }
 ```