Constructor is used to initialize objects when they are created and memory is allocated to the object.Every class has a constructor even if you specified or not.
Name of the java constructor is same as the class name and there is no return type for them.
What is a return type???
When you create any method you need to specify a return type in object oriented programming where as in procedure oriented programming like c language you need not specify mandatory return type as default return type isĀ int.
But in java you need to specify a return type in method creation.But for a java constructor is also like a method without any return type.
Method declaration and return type are as follows
When you don’t need a return type specify void
void abc(){ }
When you need String return type
String abc(){ }
same when you need int return type
int abc(){ }
like wise for every method specify a return type based on requirement.
Java Constructor :
As we discussed earlier a constructor is used to initialize object when created
There are two types of constructor’s
- Default Constructor
- Parameterized Constructor
Default Constructor:
Let’s see how consider a class Employee
Employee emp = new Employee();
Here emp is the object
new is used to create a object
Employee() is the Constructor
class Employee { String name; String empid; Employee() { name = "abc"; empid = "emp01"; } }
Now call the default constructor
public static void main(String args[]) { Employee emp = new Employee(); System.out.println(emp.name); }
class Employee { String name; Employee() { name = "abc"; } public static void main(String args[]) { Employee emp = new Employee(); System.out.println(emp.name); } }
Parameterized Constructor :
Parameterized constructor will have parameters declared in constructor.
Let’s see how it works
For you understanding
Default Constructor
Employee() { name = "abhi"; }
Parametrized Constructor
Employee(String name,String empid) { this.name = name; this.empid = empid; }
This time we will call parametrized constructor
public static void main(String args[]) { Employee emp = new Employee("abhi","emp01"); System.out.println(emp.name); }
class Employee { String name; String empid; Employee() { name = "abhi"; } Employee(String name,String empid) { this.name = name; this.empid = empid; } public static void main(String args[]) { Employee emp = new Employee("abhi","emp01"); System.out.println(emp.name); System.out.printn(emp.empid); } }