Instance Variables:
- Defining a variable inside the class and outside to methods.
- Instance variables get memory inside every object and initializes with default values.
this:
- It is a keyword and pre-defined instance variable in java.
- It is also called Default Object Reference Variable.
- “this-variable” holds object address.
- this = object_address;
- It is used to access object inside the instance methods and constructor.
Parameterized constructor:
- Constructor with parameters is called Parametrized constructor.
- We invoke the constructor in every object creation process.
- Parameterized constructor is used to set initial values to instance variables in Object creation process.
Note: We invoke the constructor with parameter values in object creation as follows
| class Test { int a; Test(int a) { this.a = a; } public static void main(String[] args) { Test obj = new Test(10); // pass value while invoking constructor } } |
Program to create two Employee objects with initial values:
| class Employee { int id; String name; double salary; Employee(int id, String name, double salary) { this.id = id; this.name = name; this.salary = salary; } void details() { System.out.println(“Emp ID is : ” + this.id); System.out.println(“Emp Name is : ” + this.name); System.out.println(“Emp Salary is : ” + this.salary); } public static void main(String[] args) { Employee e1 = new Employee(101, “Amar”, 5000); Employee e2 = new Employee(102, “Annie”, 8000); e1.details(); e2.details(); } } |