Creating instance of subclass without construstor in Java

Question

I'm facing an odd thing. Java theory says that *a subclass does not inherit any constructors from its superclass and it must provide its own. Despite this, I wrote a program that its main class generates an object without parameters (default constructor) from an subclass while in this subclass does not exist any constructors. Also, this object has initialized the attributes from its superclass. That means that the superclass has inherited its constructor to the subclass...which by the theory is wrong.

import java.util.Scanner;

public class Test {    
    public static void main(String[] args){
        Student S = new Student();
        System.out.println(S);       
    }        
}


public class Person {        
    private String name="Scarlett";  
    public String getName(){
        return name;
    }
}      


public class Student extends Person {        
    private String name="Johansson";

    /* THIS IS MISSING BUT STILL WORKING
    Student(){
       super();
    }
    */

    @Override
    public String toString(){
        return "Name is "+getName()+" Surname is "+ this.name;
    }            
}

And the Output of this code:

run:
Name is Scarlett Surname is Johansson
BUILD SUCCESSFUL (total time: 1 second)

Answer 1

If you do not define any constructor, Java, by default, will create a public, no-arg constructor that throws no exceptions, which is what you're seeing in your usecase. Once you create any constructor, regardless of its visibility, argument list or throws clause, Java will stop creating the default constructor.

Answer 2

If you are not defining a constructor in class, java will provide no argument constructor, So in your student class even u commented the constructor the constructor is provided by Java, in turn it will invoke before executing any statement in child constructor it will invoke parent class default constructor. Please see check the link..Java default constructor

Answer 3

Already correctly answered by more than one user that compiler will provide constructor. If you like to verify that by yourself use javap on Student class, should produce this output:

Compiled from "Test.java"
class Student extends Person {
  Student();
  public java.lang.String toString();
}

Even if you commented out constructor it is there. javap is in bin directory of your JDK.