#AP Computer Science A: Objects - The Night Before 🚀

Hey there! Let's get you feeling super confident for tomorrow's AP Computer Science A exam. This guide is designed to be your quick, high-impact review, focusing on the most important stuff about objects. Let's dive in!

#Unit 2: Using Objects - Overview

#Exam Weighting

• This unit is worth 5-7.5% of the exam. Expect around 2-3 multiple-choice questions.

#Enduring Understanding

Java is an object-oriented programming (OOP) language. Objects are the core of OOP, and this unit introduces them. Key OOP principles include:

• Abstraction (partly here, more in Unit 5)
• Encapsulation (Unit 5)
• Inheritance and Polymorphism (Unit 9)

#Building Computational Thinking

• You'll learn to write your first methods (like functions), which perform specific tasks.
• You'll use methods from the Math and String classes.
• You'll understand objects as reference types that represent real-world items and situations.

#Main Ideas

• Creating/Initializing Objects
• Writing/Calling Methods
• String Class & Methods
• Wrapper Classes
• Math Class

#2.1: Objects: Instances of Classes

• Objects are reference types, meaning they store a memory location rather than the actual value.
• A class is a blueprint or template for creating objects. Think of a class as a cookie cutter and an object as the cookie.
• An object is a specific instance of a class.
• Classes define the characteristics (data) and behaviors (methods) that objects of that class will have.

#2.2: Creating and Storing Objects (Initialization)

• To create an object, you use the constructor of the class.
• The constructor is called using the new keyword.
• Parameters passed to the constructor initialize the object's attributes.