How to combine multiple Comparator?

My very first post question here, be gentle please :)

I am trying to create a comparator in Java that sorts based on various criteria. The Main class is very basic, it has several variables which the sorting is based on.

For example, a "Book" class, which has :

page number,
title,
average wordcount per page.

Here is what "intructions" i was given:

Write a ComplexComperator, which can sort based on multiple variables. Make 2 constructors:

One with 2 parameters

 public ComplexComparator(Comparator<Book> x, Comparator<Book> y)

If both items are equal based on first parameter, then it sorts based on the second parameter,

And another with 4 parameters

 public ComplexComparator(Comparator<Book> x, boolean h, Comparator<Book> y, boolean i)

If the logical variables are true, it sorts it in a natural order based on that Comparator - so it works the same as the 2-parameter constructor. If one of the logical variables takes a false value, it will reverse the natural order.

So, thats it. I wrote simple Comparators but i don't know how to handle this one. I don't know what the compare method should look like; or even if I have to add some kind of class variable... Thank you for any help!

Solution

1. How to do

You may add a Comparator<Book> in your ComplexComparator class and you just need to check the different possibilities for the conditions in you constructor :

public class ComplexComparator implements Comparator<Book>{

    private Comparator<Book> comp;

    public ComplexComparator(Comparator<Book> x, Comparator<Book> y) {
        comp = x.thenComparing(y);
    }

    public ComplexComparator(Comparator<Book> x, boolean h, Comparator<Book> y, boolean i) {
        if (h && i) {
            comp = x.thenComparing(y);
        } else if (h) {
            comp = x.thenComparing(y.reversed());
        } else if (i) {
            comp = x.reversed().thenComparing(y);
        } else {
            comp = x.reversed().thenComparing(y.reversed());
        }
    }

    @Override
    public int compare(Book o1, Book o2) {
        return comp.compare(o1, o2);
    }
}

2. How to create it

If you have the correct getters you can use as

public static void main(String[] args) {
    Comparator<Book> page = Comparator.comparing(Book::getPageNb);
    Comparator<Book> title = Comparator.comparing(Book::getTitle);

    ComplexComparator c1 = new ComplexComparator(page, title);
    ComplexComparator c2 = new ComplexComparator(page, true, title, false);
}

3. How to use it

How to combine multiple Comparator?

Full Workable Demo

`Full Workable Demo`