public int[] find(String name){
        int mas = 0;
        for (int i = 0; i < book.length; i++) {
            if (book[i] != null && book[i].name.equals(name)) mas++;
        }
        int[] newmas = new int[mas];
        for (int i = 0, j= 0; i < book.length; i++) {
            if (book[i] != null && book[i].name.equals(name)) {
                newmas[j] = i;
                j++;
            }
        }
        return newmas;
    }