Object and Classes

Object: As explained earlier in the post OOPs concept, Object can be defined as what we see around us in real world like car, pen, TV etc. It can be a physical and logical entity. Every object has a state and behavior.

Take an example of Car: A car has a state (color, model, name etc.) and behavior( driving, applying break etc.). Likewise, in programming language also we create the objects which meets the requirement of business and helps in re-usability, maintainability and robustness etc.

Class: It is a blueprint, from which an object can be created. A class is a group of objects.

Along with that a class can have the following:

• Data members
• Another class
• Method
• Constructor
• block

Example of an object and class:

public class Employee {	
	String name; //Data member
	int age;   //Data member
	
	public static void main(String[] args) {
		Employee emp = new Employee();  // creating the object of Employee
		System.out.println(emp.name);   //print name 
		System.out.println(emp.age);    //print age
	}	
}

Let’s take one more example , where we are creating the methods and calling that method by using 2 created objects emp1, emp2.

New keyword is used to create the object which assigns memory to it at run time.

public class Employee {	
	String name; //Data member
	int age;   //Data member
	
	public void displayRecord(String empName,int empAge){   // method
		name =empName;
		age =empAge;
		
		System.out.println(name +"---" + age);
	}
	
	public static void main(String[] args) {
		Employee emp1 = new Employee();  // creating the object of Employee
		Employee emp2 = new Employee();  // creating another object of Employee
		
		emp1.displayRecord("Employee 1", 25);
		emp1.displayRecord("Employee 2", 30);

	}	
}