A constructor is a special type of method that initializes an object. It has the same name as the class and does not have a return type. There are two types of constructors: a default constructor with no arguments, and a parameterized constructor with one or more arguments. A constructor initializes the state of an object when it is created, while a method exposes the behavior of an object and can have a return type. Constructors are invoked implicitly when an object is created using the new keyword.

1. Java Constructors
BY MARCO ALZAMORA

2. What is a Constructor
• A CONSTRUCTOR IS A SPECIAL TYPE OF METHOD THAT IS USED TO IINITIALIZE AN OBJECT.
• THEY DO NOT CONTAIN ANY RETURN TYPE.
• THEY HAVE THE SAME AS THE CLASS.

3. Types of Constructors
Default Constructor (contains no arguments
Parameterized constructor (One or more arguments)

4. Default Constructor
 Example:
Class Car {
Car()
{
System.out.println(“Constructor has been created”);
}
Public static void main(String args[])
{
Car c = new Car();
}
}
The keyword new
creates the Car object
and invokes the
constructor to initialize
the object created

5. Parameterized constructor
public class Student {
int stuId;
String stuName;
//parameterized constructor with two parameters
Student ( int id, String name ){
stuId= id;
stuName = name;
}
void info(){
System.out.println("Id: "+stuId+" Name: "+stuName);
}
public static void main(String args[]){
Employee obj1 = new Student(00015,“Smith");
Employee obj2 = new Student(00017,“Watson");
obj1.info();
obj2.info();
}
}
Two objects created: obj1, and
obj2
Constructor same name as
the class with two
parameters
Call the obj1, obj2 instances of the
class student
Void method of the
class Student

6. Difference between a constructor and
a method
Constructor Method
Constructor is used to initialize the
state of an object.
Method is used to expose the
behavior of an object.
Constructor must not have return
type.
Method must have a return type.
Constructor name must be same as
the class name.
Method name should not be the same
as the class name.
Constructor is invoked implicitly. Method is invoked implicitly.