public class Library {
    private Object[] holdings;
    private int count;

    public Library(int size) {
        if (size < 1) {
            throw new IllegalArgumentException("invalid capacity");
        }
        holdings = new Object[size];
        count = 0;
    }

    public void add(Object item) {
        for (int i = 0; i < count; i++)
            if (holdings[i].equals(item))
                return;
        holdings[count] = item;
        count++;
    }

    public String toString() {
        String s = "Library:\n";
        for (int i = 0; i < count; i++)
            s += holdings[i] + "\n";
        return s;
    }

    public static void main(String[] args) {
        Library lib = new Library(10);
        lib.add(new Book("War and Peace", 1000));
        lib.add(new Book("War and Peace", 1000));
        lib.add(new Video("Pirates of Silicon Valley", 105));
        System.out.println(lib);
    }

}