I‘m get confused with super() usage

Question

I know super() is used to retrieve the instance variables from parent class, but when I saw the codes as follow:

public class novel extends literature {
private String title;
private String writer;
public novel(String title)
{
    super("novel");
    this.title = title;
    this.writer = "Unknow";
}
public novel(String title, String writer)
{
    super("novel");
    this.title = title;
    this.writer = writer;
}
public String getInfo()
{
    return getGenre() + "\nTitle: " + title + "\nWriter: " + writer;
}
public static void main(String[] args)
{
    novel n = new novel("The devil wears prada", "Lauren Weisberger");
    System.out.println(n.getInfo());
}

}

When I saw this: super("novel"); I get very confuse, how come the child class name can be put in the super method? And I don't know why this.writer = "unknown"; is here for what? Why don't it just set it to be writer?

Sorry for throwing so many questions to you guys, but will appreciate a lot for any solutions.

I'm sorry guys i still did not totally get why it used super("novel")? If we say novel here is a string, but then why we use that string which has the same name as "novel class"?

Answer 1

super ("novel") means that you pass a String as argument for the constructor of the parent class.

this.writer = "Unknow" means that you pass the String value "Unknow" to a member of the current class instance. You could also pass eg. "Mark Twain", the writer's variable value will then be "Mark Twain".

For more information http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html

Example

//Parentclass

public class Book {

private String genre;
private String isbn;

//As you can see we have two constructors.

//The first with only one argument
public Book (String genre)
    this.genre = genre;
}


//The second one with two arguments
public Book (String genre, String isbn) {
    this.genre = genre;
    this.isbn = isbn;
}

}

//subclass
class Novel extends Book{

public Novel(String isbn)
   
   
   super("novel", isbn);
   //super() has now two arguments, because we are calling the second constructor
   //which has two args. 
   //Now, in the parent class members genre = "novel" and isbn equals the value passed in the
   //child constructor.
   //This is the same as using the parent constructor inner body in this constructor. 
   //Normally the parent constructor gets overwritten on inheritance. 
   //But super makes its possible to use the parent constructor. 


}

For more examples check this super() documentation