Constructors

Tips

• If you put void ahead of constructor name, it comes a method i.e when we call the class’s constructor with new ahead of it; this void constructor will not be called, instead you can call this as a normal method using dot . operator.
• Constructor implicitly returns the instance of the class
• Constructor cannot be inherited
• Constructor cannot be final
• Constructor can be overloaded but cannot be overriden
• No Copy constructor in java but you can copy using
  • Creating a constructor that copies each value from an object
  • Copying the reference to another
  • By using clone

Rules for creating Java constructor

1. Constructor name must be the same as its class name
2. A Constructor must have no explicit return type
3. A Java constructor cannot be abstract, static, final, and synchronized

Types of Java constructors

1. Default constructor (no-arg constructor)
   • A constructor is called “Default Constructor” when it doesn’t have any parameter.
   • The default constructor is used to provide the default values to the object like 0, null, etc., depending on the type.
2. Parameterized constructor
   • Constructor which has parameter is called parameterised constructor.

Constructor Overload

• Constructor overloading a technique where we can have any number of constructor with different parameter list.

Difference between constructor and method.

Java Constructor	Java Method
A constructor is used to initialize the state of an object.	A method is used to expose the behavior of an object.
A constructor must not have a return type.	A method must have a return type.
The constructor is invoked implicitly.	The method is invoked explicitly.
The Java compiler provides a default constructor if you don’t have any constructor in a class.	The method is not provided by the compiler in any case.
The constructor name must be same as the class name.	The method name may or may not be same as the class name.

To add :

• How new creates a new object via constructor in java
• Condition in which you are required to add a constructor in java

Important things to be noted for constructor

• Method with the same name as constructor can be created and no compile time or runtime exception will occur.