Object-oriented programming (OOP) is a programming paradigm that uses objects to represent real-world entities and their interactions. In Java, a class is a blueprint or a template that defines the properties and behavior of an object. In this blog post, we’ll discuss the OOP class in Java in detail, including its syntax, properties, and methods, with examples.

Syntax of a Java class

The syntax of a Java class is as follows:

[access_modifier] class ClassName [extends SuperClassName] [implements InterfaceName]
{
  // Fields
  // Constructors
  // Methods
}

Access modifier specifies the level of access to the class, and it can be public, protected, or private. ClassName is the name of the class, and it should start with a capital letter. The extends keyword is used to inherit properties and behavior from a parent class or a superclass. The implements keyword is used to implement the methods of an interface.

Properties of a Java class

A Java class can have the following types of properties:

1. Instance variables: These are non-static variables that belong to an object. Each object of the class has its own set of instance variables.
2. Static variables: These are class-level variables that belong to the class rather than an object. They are shared by all objects of the class.
3. Final variables: These are constants that cannot be changed once initialized.
4. Transient variables: These are variables that are not serialized when an object is written to a file.
5. Volatile variables: These are variables that are accessed by multiple threads, and their value is always read from main memory.

Methods of a Java class

A Java class can have the following types of methods:

1. Constructors: These are special methods that are used to create objects of the class. They have the same name as the class and do not have a return type.
2. Instance methods: These are non-static methods that belong to an object. They can access instance variables and can modify their values.
3. Static methods: These are class-level methods that belong to the class rather than an object. They cannot access instance variables and can only access static variables.
4. Getter and setter methods: These are methods used to get and set the values of instance variables.

Example of a Java class

Here’s an example of a Java class that defines a Circle object:

public class Circle {
  private double radius;

  public Circle(double radius) {
    this.radius = radius;
  }

  public double getRadius() {
    return radius;
  }

  public void setRadius(double radius) {
    this.radius = radius;
  }

  public double getArea() {
    return Math.PI * radius * radius;
  }

  public double getCircumference() {
    return 2 * Math.PI * radius;
  }
}

In this example, the Circle class has one instance variable, radius, which is a double value. The class has a constructor that takes a radius parameter and initializes the radius instance variable. The class also has getter and setter methods for the radius instance variable. Finally, the class has two methods, getArea() and getCircumference(), that return the area and circumference of the circle, respectively.

In conclusion, a class in Java is a blueprint that defines the properties and behavior of an object. It can have instance variables, static variables, final variables, transient variables, and volatile variables, and it can have constructors, instance methods, static methods, getter and setter methods, and other types of methods. Understanding classes is an essential part of object-oriented programming in Java, and it’s important to use them effectively to create well-structured and maintainable code.