Creating and Storing Objects (Instantiation) Quiz

Study Notes

OOP Concepts in Java

In Java, a class can have both instance variables and class variables.
When methods in a superclass and subclass have the same name and signature, they are called overridden methods.

Class and Object Definitions

A class is a blueprint or design for real-life objects.
An object is an instance of a class, containing data and program code.
A class is considered a design for real-life objects.

Class Composition

A class in Java is generally made up of four components: attributes, methods, objects, and constructors.
Attributes are used to describe the properties of an object, and are defined by variables in a class.
Methods are used to access or modify attributes of a class.

Class Declaration and Instantiation

The syntax for declaring a class object is: Classname objectname;
The keyword new is used to create an object by allocating memory, which is termed as instantiation.
A constructor is called to initialize the newly created object, which is termed as construction.

Memory Allocation

Objects live in a special portion of the memory called the heap.
Reference is the address of the memory location where the object is stored.

Object Creation

In object-oriented programming (OOP) languages, creating an object is called instantiation.
The syntax for creating an object is: Classname objectname = new Classname();

Accessing Class Members

Instance variables and instance methods are accessed via objects.
The syntax for accessing methods or variables of a class is: objectname.methodname() or objectname variablename.

Class Variables and Methods

Class variables and class methods are defined using the static keyword.
Class methods can be called without creating an instance of a class.

Method Overloading and Constructors

When more than one method has the same name but different parameters, it is called method overloading.
A constructor is invoked automatically when an object is created.
The super keyword is used to refer to a superclass constructor in a subclass constructor.

Description

Test your knowledge on classes and objects in Java with this quiz! Questions cover topics such as defining attributes and methods, declaring class variables and methods, creating objects, and calling methods without creating instances.