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Java Constructors

Constructor

• Constructor in java is a special type of method that is used to initialize the object

• Java Constructor is invoked at the time of object creation• They do not contain any return type• Constructor name is same as class name


Types of Constructors

• Default constructor (no-arg constructor)• Parameterized constructor

Types of constructors

Default constructor Parameterized constructor


Default Constructors

Example for default constructor:

class Cons{ cons(){System.out.println("constructor is created");

} public static void main(String args[]){ Cons c=new Cons();

} }


Parameterized Constructors

Example for parameterized constructor

class Student4{ int id; String name; Student4(int i,String n){ id = i; name = n; } void display(){System.out.println(id+" "+name);}

public static void main(String args[]){ Student4 s1 = new Student4(111,"Karan"); Student4 s2 = new Student4(222,"Aryan"); s1.display(); s2.display(); }

}


Difference between constructor and method

Constructor Method

Constructor is used to initialize the state of an object.

Method is used to expose behaviour of an object.

Constructor must not have return type

Method must have return type.

Constructor is invoked implicitly.

Method is invoked explicitly.

Constructor name must be same as the class name.

Method name should not be same as class name


Constructor Overloading

• Constructors are methods that can be overloaded, just like any othermethod in a class.

• Constructors having the same name with different parameter list iscalled constructor overloading.


Topics Covered during Training

• Classes, Objects, Keywords, Methods• Exception Handling• String Handling• Multithearding• AWT• Swing• Applet• Collections• Hibernate• Struts etc………………


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