What is constructor? Explain various types of constructor in details code example

Example 1: default constructor java

Default constructor is a constructor created by compiler; if user does not 
create a constructor in a class.
If user defines a constructor in a class then java compiler will not create 
default constructor.

Example 2: what is constructor in java

A constructor is a special method used to initialize objects in java.
we use constructors to initialize all variables in the class 
when an object is created. As and when an object
is created it is initialized automatically with the help of 
constructor in java.
  
We have two types of constructors:
Default Constructor
Parameterized Constructor

public classname(){
}
public classname(parameters list){
}