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 is 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);
}
}