Java Class and Object

12 Mar 2023


Java Classes and Objects are essential when it comes to understanding Java programming. Java objects are similar to real-world objects. They have states, behaviors, and attributes. Java classes allow programmers to model their code after a metaphor of the real world. Java classes also contain variables and methods; variables capture the state of an object, while methods dictate its behavior. Java Classes and Objects work together to form the core of Java's powerful object-oriented programming capabilities that make coding more straightforward and intuitive. Java's strong focus on both Objects and Classes makes it a sound choice for anyone looking to learn a new programming language!

Java Class

A java class is a building block of java programming language that encapsulates a set of objects with the same characteristics. It defines the data and behavior associated with the class, serving as an outline of what the objects it creates will contain. Java classes provide structure to java programs and are essential for java developers to be able to use the language accurately and efficiently. An object is an abstract concept in java; it has no physical representation like variables or other types of data but instead acts as a template for entities being modeled within a program. It is via java classes that these models can be made by introducing structure and other elements such as inheritance, polymorphism, abstraction, and encapsulation. Ultimately, java classes will form the script from which objects are created: without them, java development would be virtually impossible.


access_modifier class<class_name>
    data member; 
    nested class;


class Student {
 int id; // data member (also instance variable)
 String name; // data member (also instance variable)

 public static void main(String args[])
  Student s1 = new Student(); // creating an object of
         // Student

How to create a class in java

Creating a class in Java is a simple yet powerful tool in the programming language. It involves listing classes, defining class variables and methods, and creating objects with the design of the java class. The create class process starts with writing the code for a java file, making sure to specify that it is a public class. This allows other programs to find what that particular program consists of and how it should be used. After completing this step, create as many variables and methods as needed for the program. Finally, create an object from the original public java class and access its variables or methods for use in that application. With this information at hand, anyone can create Java classes efficiently with only a few steps to follow.

Object in java

Object in Java is an important concept to understand when learning the Java programming language. Object in Java allows programmers to store and process data, making it a powerful and popular programming language. Object in Java consists of a hierarchy of classes that are used to create and define different types of objects which can then be manipulated by code. Object in Java is also used for Object Oriented Programming (OOP) as it enables programmers to break down complex problems into smaller subproblems that can be solved independently. Object in java can be reused easily, allowing developers to save time and avoid rewriting the same code multiple times. Object in java is versatile and easy to learn, making it a great choice for beginners and experienced coders alike.

How to create an object in java

Define a class:

First, the user needs to define a class that describes the object the user wants to create. The class is a blueprint for the object.
For example, if the user wants to create an object of a Car class, can define a Car class as follows:
public class Car {
   // Class variables
   String color;
   int modelYear;
   // Class constructor
   public Car(String color, int modelYear) {
      this.color = color;
      this.modelYear = modelYear;
   // Class methods
   public void start() {
      System.out.println("The car is starting.");
   public void stop() {
      System.out.println("The car is stopping.");

Create an instance of the class:

Once the developers have defined the class, then anyone can create an instance of the class by using the "new" keyword.
For example, to create an instance of the Car class, can do the following:
Car myCar = new Car("red", 2022);
This will create a new instance of the Car class with the color "red" and model year 2022, and assign it to the variable "myCar".

Access the object:

Once the developers have created the object, then the user can access its variables and methods by using the dot (.) notation.
For example, to access the color variable of the "myCar" object, anyone can do the following:
String carColor = myCar.color;
This will assign the value of the "color" variable of the "myCar" object to the "carColor" variable.
Similarly, to call the "start" method of the "myCar" object, anyone can do the following:
This will call the "start" method of the "myCar" object, which will print the message "The car is starting." to the console.

Different ways to create objects in java

Using the new keyword: 

The developer can create an object of a class using the new keyword followed by the constructor of the class.


ClassName objectName = new ClassName();

Using Class.forName() method: 

The developer can create an object of a class using the Class.forName() method, which returns a Class object.


Class className = Class.forName("ClassName");
ClassName objectName = (ClassName) className.newInstance();

Using clone() method:

The programmers can create a new object by cloning an existing object using the clone() method.


ClassName object1 = new ClassName();
ClassName object2 = object1.clone();

Using object deserialization: 

The programmers can create an object by deserializing the object from a file or network stream


ObjectInputStream objectInputStream = new ObjectInputStream(inputStream);
ClassName objectName = (ClassName) objectInputStream.readObject();

Using Factory Method:

Developer can use a Factory Method to create objects of a class by calling a method that returns an instance of the class.


public static ClassName createObject() {
    return new ClassName();
ClassName objectName = ClassName.createObject();

Using Dependency Injection:

User can create objects by injecting dependencies into the class constructor or using a framework to manage object creation.


public class MyClass {
    private Dependency dependency;
    public MyClass(Dependency dependency) {
        this.dependency = dependency;
MyClass objectName = new MyClass(new Dependency());

Anonymous object in java

Anonymous objects in Java are incredibly useful for instantiating an object and using it within a single statement. They are typically used when an object is needed briefly, such as during method or constructor calls. These objects can be used to call methods or access fields without explicitly creating a variable for it, and often make coding simpler. Anonymous objects provide flexibility since many abstract classes do not require concrete implementations. Anonymous objects are incredibly practical when it comes to streamlining code and simplifying scripting through their ability to hide complexity and provide clean output with just the information required by the programmer.
btn.setOnAction(new EventHandler()
    public void handle(ActionEvent event)
        System.out.println("Hello World!");
Parameter Class Object
Definition: A class is a blueprint or a template that defines the properties and behavior of objects. An object is an instance of a class that has actual values for those properties.
Usage: A class is used to create objects, which are instances of that class. An object is an instance of a class that has been created using the constructor of that class.
Properties: A class defines the properties that objects of that class will have. These properties are defined using variables. An object has values for those properties.
Methods: A class also defines the behavior that objects of that class will have. This behavior is defined using methods. An object can call these methods to perform specific tasks.
Memory allocation:A class is not allocated memory in the Java Virtual Machine (JVM).An object is allocated memory when it is created using the "new" keyword.

To wrap up, Java Class and Object is a powerful concept that can help create efficient code. It is important to become familiar and comfortable with the nuances of this fundamental object-oriented programming language feature in order to be able to utilize its full potential. There are plentiful resources online - tutorials, guides, references - to help get started and gain greater insight into the concepts. Through practice and collaboration, one can grow significantly as a programmer by mastering the fundamentals like Java Class and Object. So take the opportunities presented today to learn how to better your ability with Java Class and Object, you will not regret it!

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