how do u take a class as a constructor code example

Example 1: 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){
}

Example 2: type of constructor in java

There are three types of constructors: 
Default, No-arg constructor and Parameterized.
  
If you do not implement any constructor in your class,
Java compiler inserts a default constructor into your code on your behalf.
This constructor is known as default constructor.
  
Constructor with no arguments is known as no-arg constructor

Constructor with arguments(or you can say parameters) is known as 
Parameterized constructor.