Constructors are special methods used to initialize objects. They do not have a return type and their name is the same as the class name. There are two types of constructors: default constructors that contain no arguments, and parameterized constructors that contain one or more arguments to initialize an object's fields. The new keyword is used to create an object and invoke its constructor. Constructors initialize an object's state while methods expose its behavior.

1. Java Constructors
BY MARCO ALZAMORA

2. What is a Constructor
• A CONSTRUCTOR IS A SPECIAL TYPE OF METHOD
THAT IS USED TO INITIALIZE 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.