Instanceof doesn't return right answer

Question

On Android I have 3 class

GENERALBOOK

public class General_Book {
protected String Titolo;
protected int Tag;

public General_Book(String t, int i) {
    Titolo = t;
    Tag=i;
}

public General_Book() {
    //
}

public void setTitolo(String t) {
    Titolo=t;
}
public void setTag(int i) {
    Tag=i;
}
public String getTitolo() {
    return Titolo;
}
public int getTag() {
    return Tag;
}
}

MOSTBOOK

public class Most_Book extends General_Book {
private String SubTitolo;
private float Rating;

public Most_Book(String t,String s,float d, int c) {
    super(t,c);
    SubTitolo=s;
    Rating=d;
}
public void setSubTitolo(String t) {
    SubTitolo=t;
}
public void setRating(float c) {
    Rating=c;
}
public String getSubTitolo() {
    return SubTitolo;
}
public float getRating() {
    return Rating;
}
}

and TOPBOOK

 public class Top_Book extends General_Book{
private String Incipit;
private String imageUri;
public Top_Book(String t,String i,String u, int c) {
    super(t,c);
    Incipit=i;
    imageUri=u;
}
public Top_Book() {

}
public void setIncipit(String i) {
    Incipit=i;
}
public void setImageURI(String u) {
    imageUri=u;
}
public String getIncipit() {
    return (Incipit.length()>120) ? Incipit.substring(0, 117) + "..." : Incipit;

}
public String getImageURI() {
    return imageUri;
}
  }

Now on activity I have 2 ListView one with a TopBook and another one with MostBook I created a CustomArrayAdapter that manages both type but it doesn't work as I expect Because always enter in first IF of "instanceof", and I have no idea why, could you help me and explain what I'm doing wrong?

CUSTOMARRAYADAPTER

 public class CustomArrayGeneralBook extends ArrayAdapter<General_Book> {
private final LayoutInflater mInflater;
public ImageLoader imageLoader;
public CustomArrayGeneralBook(Context context,General_Book[] tops) {
    super(context,android.R.layout.simple_list_item_2,tops);
    mInflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
    imageLoader = new ImageLoader(context);
}


@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View view;
    if (convertView == null) {
        view = mInflater.inflate(R.layout.fragment_home_child_mostbook, parent, false);  
    } else {
        view = convertView;
    }
    Object o = getItem(position);
    if(o instanceof General_Book) {
        Log.e("A","QUI");
        General_Book item = getItem(position);
        view.setTag(item.getTag());
    }
    else if (o instanceof Most_Book) {
        Log.e("A","QUI2");
        Most_Book item = (Most_Book) getItem(position);
        ((TextView)view.findViewById(R.id.most_book_title)).setText(item.getTitolo());
        ((TextView)view.findViewById(R.id.most_book_subtitle)).setText(item.getSubTitolo());
        ((RatingBar)view.findViewById(R.id.most_book_ratingbar)).setRating(item.getRating());
        view.setTag(item.getTag());
    }
    else if (o instanceof Top_Book) {
        Log.e("A","QUI3");
        Top_Book item = (Top_Book) getItem(position);
        ((TextView)view.findViewById(R.id.top_book_title)).setText(item.getTitolo());
        ((TextView)view.findViewById(R.id.top_book_incipit)).setText(item.getIncipit());
        imageLoader.DisplayImage(item.getImageURI(), (ImageView)view.findViewById(R.id.top_book_cov));
        view.setTag(item.getTag());
    }       
    return view;
}
 }

EDIT Ok, that works at the end with anwser I accepted, just to clarify everyone:
I had to add a different Inflater.inflate(R.layout....) in each if to do not crash app :)
Thank you

Answer 1

An instance of Most_Book is also an instance of General_Book, because Most_Book extends General_Book. (same goes for Top_Book).

In your case, you need to test for the most specific values first:

if(o instanceof Most_Book) {
     //...
} else if (o instanceof Top_Book) {
     //...
} else if (o instanceof General_Book) {
    //...
}

Answer 2

I believe you need to place the ifs the other way . Because if o is an instance of Most_Book, General_Book or Top_Book it will enter the first if.General_Book is the parent class of Top_Book and Most_Book an is the most generalized one . Start the if() check with the specialized ones and then move towards the generalized ones.

if(o instanceof Top_Book) {
 //...
} else if (o instanceof Most_Book) {
 //...
} else if (o instanceof General_Book) {
//...
}

Refer JLS 15.20.2

At run time, the result of the instanceof operator is true if the value of the RelationalExpression is not null and the reference could be cast (§15.16) to the ReferenceType without raising a ClassCastException. Otherwise the result is false.

If o is an instance of Top_Book or Most_Book , then the below is fine.

General_Book b = o;

Hence if(o instanceof General_Book) will always be true.