Unit 5: Arrays and ArrayLists
Arrays
- Array: A fixed-size data structure that stores elements of the same data type.
- Declaration: Create an array and specify its type and size.
int[] numbers = new int[5];
- Initialization: Set values for array elements.
numbers[0] = 1; numbers[1] = 2;
- Accessing Elements: Access elements by their index.
int firstNumber = numbers[0];
ArrayLists
- ArrayList: A dynamic-size data structure that stores objects of a specified data type.
- Declaration and Initialization: Create an ArrayList and add elements.
ArrayList<String> names = new ArrayList<>(); names.add("Alice"); names.add("Bob");
- Accessing Elements: Get elements by index or use iteration.
String firstPerson = names.get(0); for (String name : names) { // Code to process each name }
Unit 6: Object-Oriented Programming
Classes and Objects
- Class: A blueprint for creating objects, defining attributes and methods.
class Car { String make; int year; // Methods and constructors }
- Object: An instance of a class created using the
new
keyword.Car myCar = new Car(); myCar.make = "Toyota"; myCar.year = 2022;
Constructors
- Constructor: Special method to initialize objects when created.
class Car { String make; int year; Car(String make, int year) { this.make = make; this.year = year; } }
Inheritance
- Inheritance: A mechanism where a subclass can inherit attributes and methods from a superclass.
class Animal { void eat() { // Code for eating } } class Dog extends Animal { void bark() { // Code for barking }
Polymorphism
- Polymorphism: Allows objects of different classes to be treated as objects of a common superclass. It supports method overriding.
class Animal { void makeSound() { // Default animal sound } } class Dog extends Animal { @Override void makeSound() { // Dog's sound }