cevaplar

15.

abstract public class Book {
    public String title;
    public int rating;
    public Book(String title){
       
        rating = 0;
    }
    public void setRating(int rating){
        // rating must be between 0 and 5
        if(rating>0 && rating <5)
            this.rating = rating;
    }
    public void setTitle(){
        this.title = title;
    }
    public String getTitle(){
        return title;
    }
    public abstract void print();
}

16.

public class Novel extends Book{
    private String mainChar;
    public Novel(String title){
        super(title);
    }
    public void setMainChar(String character){
        mainChar = character;
    }
    public String getMainChar(){
        return mainChar;
    }
    public void print(){
        System.out.println(title+" "+rating+" "+mainChar);
    }
}

17.

public class TechnicalBook extends Book{
    private int revisionNum;
    public TechnicalBook(String title){
        super(title);
        revisionNum = 1;
    }
    public void newRevision(){
        if(revisionNum>0)
            revisionNum++;
    }
    public void print(){
        System.out.println(title+" "+rating+" "+revisionNum);
    }
}