Check out example codes for "default constructor java". It will help you in understanding the concepts better.

Code Example 1

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.

Code Example 2

class NoteBook{
   /*This is default constructor. A constructor does
    * not have a return type and it's name
    * should exactly match with class name
    */
   NoteBook(){
      System.out.println("Default constructor");
   }
   public void mymethod()
   {
      System.out.println("Void method of the class");
   }
   public static void main(String args[]){
	/* new keyword creates the object of the class
         * and invokes constructor to initialize object
         */
	NoteBook obj = new NoteBook();
	obj.mymethod();
   }
}

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