Classes and Objects Flashcards
A high-level, powerful programming language that
uses the Object-Oriented Programming (OOP)
approach.
Java
A programming style that models real-world entities as “objects.”
Object-Oriented Programming (OOP)
Objects have: (mention 2)
Data (fields): Information or attributes.
Behavior (methods): Actions or functions.
Objects have:
Data (fields): ______________
Behavior (methods): _____________
Data: Information or attributes.
Behavior: Actions or functions.
Programs are written as step-by-step instructions or
functions.
Traditional Programming (Procedural)
What is a Class?
A class is like a blueprint or template for creating
objects.
Mention two Variables in a Class:
Instance Variables
Class Variables
What type of variable is this in a class?
* Declared inside a class but outside any method.
* Non-static and unique to each object.
Instance variables
What type of variable is this in a class?
* Declared with the static keyword.
* Shared across all objects of the class.
Class variables
An ________ is a real-world entity created from a class.
object
If a ______ is a blueprint, an object is the actual
product made from that blueprint.
class
The process of creating an object
from a class.
Instantiation
___________ are the characteristics or properties of
an object.
Attributes
Attributes are also called ________ or ________
variables.
fields or instance
variables.
Do attributes belong to a class? True or false
True
Each object has its own copy of class
variables. True or false
False
Each object has its own copy of instance
variables not class variables.
_________ variables are specific to an object
and can only be accessed within that
object.
Instance
Java reserves ________ for the object based on the class blueprint.
memory
The name of the class.
ClassName
The name of the object (instance).
objectName
This keyword allocates memory for the object.
new
Calls the class constructor to initialize the object.
ClassName()
We can create ___________ attributes (which belong to individual objects) and ________ attributes (which belong to the class itself)
non-static , static
To access the attributes of a class, we create an ________ and use _____________.
object , dot notation (.)
A special method used to initialize objects when they are created.
Constructor
A constructor is a special method used to _________ objects when they are created.
initialize
It has the same name as the class and runs automatically during object instantiation.
Constructor
What are the 2 types of Constructors?
1.Default Constructor (No Parameters)
2. Constructor with Parameters
Assigns default values to object attributes.
Default Constructor
Allows assigning custom values when creating an object.
Constructor with Parameters
Default Constructor has list of parameters. True or false?
False
Default constructor has no parameter.
What are the types of access modifiers?
● Public: Accessible everywhere.
● Private: Accessible within the class only.
● Protected: Accessible within the package and subclasses.
● Default: Accessible within the package.
● __________: Accessible everywhere.
● __________: Accessible within the class only.
● __________: Accessible within the package and subclasses.
● __________: Accessible within the package.
● Public: Accessible everywhere.
● Private: Accessible within the class only.
● Protected: Accessible within the package and subclasses.
● Default: Accessible within the package.
Multiple methods with the same name but different parameters.
Method Overloading
Wrapping data and methods into a single unit.
Encapsulation
One class acquires properties and methods of another class.
Inheritance
Refers to parent class members.
super Keyword
Ability to take multiple forms.
Polymorphism
Two types of Polymorphism:
Compile-time (Method Overloading)
Runtime (Method Overriding)
- Hiding implementation details and showing functionality.
- Achieved through Abstract Classes and Interfaces.
Abstraction
- Cannot be instantiated.
- Can have abstract and non-abstract methods.
Abstract class
- It is a collection of abstract methods.
- It also Implements multiple inheritance.
Interface
final Keyword:
● _________: Constant value.
● _________: Cannot be overridden.
● _________: Cannot be inherited.
● Final Variable: Constant value.
● Final Method: Cannot be overridden.
● Final Class: Cannot be inherited.
Superclass of all classes in Java.
Object Class
. Type Casting
● _________: Subclass to Superclass.
● _________: Superclass to Subclass.
● Upcasting: Subclass to Superclass.
● Downcasting: Superclass to Subclass
instanceof Operator:
* Checks if an object is an instance of a class. (visualize the syntax to answer)
if (obj instanceof ClassName) {}
Group of related classes and interfaces
Packages
Used to include packages.
import keyword
Accessing Package Members
- Fully Qualified Name or ________________.
Import Statement
Mechanism to handle runtime errors.
Exception Handling
Automatic memory management.
Garbage Collection
Convert primitive data types into objects.
Wrapper Classes
Immutable sequence of characters.
String Class
Collection of similar type elements.
Arrays
Resizable array implementation.
Array list Class
Stores key-value pairs.
HashMap Class
Reading and writing files.
File handling
Concurrent execution of two or more threads.
Multithreading
Converting an object into byte stream.
Serialization
OOP enhances code _________, ____________, ___________.
reusability, security, and modularity
Method overloading allows a class to have ___________ with the same ________ but different ____________.
multiple methods, same name but different parameter list
Retrieves the value of a private variable.
Accessor (Gate)
Modifies the value of a private variable with validation.
Mutator (Setter)
Variables or methods can only be accessed within the same class.
Private Access
