how to use super class method in java

1class Parentclass
2{
3   //no-arg constructor
4   Parentclass(){
5	System.out.println("no-arg constructor of parent class");
6   }
7   //arg or parameterized constructor
8   Parentclass(String str){
9	System.out.println("parameterized constructor of parent class");
10   }
11}
12class Subclass extends Parentclass
13{
14   Subclass(){
15       /* super() must be added to the first statement of constructor 
16	* otherwise you will get a compilation error. Another important 
17	* point to note is that when we explicitly use super in constructor
18	* the compiler doesn't invoke the parent constructor automatically.
19	*/
20	super("Hahaha");
21	System.out.println("Constructor of child class");
22
23   }
24   void display(){
25	System.out.println("Hello");
26   }
27   public static void main(String args[]){		
28	Subclass obj= new Subclass();
29	obj.display();	 
30   }
31}