Java Class Syntax

A class is a fundamental building piece in object-oriented programming. It can be characterised as a template that outlines the information and actions connected to the creation of a class. A class can be instantiated to produce an object (variable) that can be used to access its member variables and methods.

A class may also be used as a conceptual template to build objects with shared attributes and operations.

For instance, all the information about an employee may be presented in the form as properties & methods in the Employee class. We can access all of the class's methods or properties if indeed the class is instantiated, or if an object (let's say e1) of the class is formed.

Defining a Class in Java

Java offers the reserved keyword class for class definitions. The class name must come after the keyword. We declare variables and methods inside the class.

The following elements are often included in class declarations in the following order:

• Modifiers: A class may have default access or be made public.
• class keyword: A class is created with the class keyword.
• Name of the class: The name must start with a letters(capitalized by convention).
• Superclass (if any): If there is one, the term extends is followed by the name of the superclass. Only one parent can be extended (subclassed) by a class.
• (If any) interfaces a list of the interfaces that the class, if any, implements, separated by commas, should be included. A class may support several interfaces.
• Body: A brace-encircled image of the class.

Syntax:

<access specifier> class Name  
{  
// variables in the class
// methods in the class
}  

Example 1 of a Java Class Let's look at the example below to see how to create a subclass in Java and use an object of the class to implement it.

Maths.java

// Imporating all the requried packages
import java.io.*;


// defining a class Maths 
public class Maths {  
     
   // Defining the variabled x and y 
   int x;  
   int y;  
  
   // Initializing the class variables 
   public Maths (int x, int y) {  
      this.x = x;  
      this.y = y;  
   }  
  
   // This method performs the addition operation
   public int addnum () {  
      int ans = x + y;  
      return ans;  
   }  
  
   // This method performs the subtraction operation
   public int sub () {  
      int ans = x - y;  
      return ans;  
   }  
  
   // This method performs the multiplication operation  
   public int mult () {  
      int ans = x * y;  
      return ans;  
   }  
  
   // This method performs the division operation  
   public int div () {  
      int ans = x / y;  
      return ans;  
   }  
  
  
   // main method starts here  
   public static void main(String[] args) {  
      // object creation for the maths class
      Maths obj = new Maths(10, 30);  
        
      // calling the methods of Maths class  
      System.out.println("Addition of two numbers is :" + obj.addnum());  
      System.out.println("Subtraction of two numbers is :" + obj.sub());  
      System.out.println("Multiplication of two numbers is :" + obj.mult());  
      System.out.println("Division of two numbers is :" + obj.div());  
  
   }
   }  

Output:

Addition of two numbers is : 40
Subtraction of two numbers is : -20
Multiplication of two numbers is : 300
Division of two numbers is : 3

Example 2:

The classes Employee & EmployeeClass are being created in the example below. The employee details are retrieved and shown by the employee class. We construct objects of the Employee class in the EmployeeClass using its methods. Here, we're utilising the class function Object () { [native code] } to initialise the objects.

Emp.java

// defining a class emp
class Emp {  
    // declaring variables  
    int eid;  
    String n;  
    String bran;  
    float income;  
  
    // Initializing the class variables 
    void intial (int id, String n, String d, float sal) {  
        this.eid = id;  
        this.n = n;  
        this.bran = d;  
        this.income = sal;  
    }  
  
    // Displaying employe details using show method  
    void show() {  
        System.out.println("Employe id is : " + eid );  
        System.out.println("Employe name is " + n );  
        System.out.println("Employe department is : " + bran );  
        System.out.println("Employe income is : " + income );  
    }  
}  
  
public class EmployeeClass {  
    // main method starts here  
    public static void main(String[] args) {  
        // object creation for the Emp class 
    Emp o1 = new Emp();    


  
    // calling the methods of Emp class    
    o1.intial (1, "Manoj", "Software", 95000);    
      
    o1.show();    
    }  
}  

Output:

Employe id is : 1
Employe name is Manoj
Employe department is : Software
Employe income is : 95000