Grouping by object value, counting and then setting group key by maximum object attribute

Question

I have managed to write a solution using Java 8 Streams API that first groups a list of object Route by its value and then counts the number of objects in each group. It ret

Answer 1

Changed equals and hashcode to be dependent only on start cell and end cell.

@Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;

        Cell cell = (Cell) o;

        if (a != cell.a) return false;
        if (b != cell.b) return false;

        return true;
    }

    @Override
    public int hashCode() {
        int result = a;
        result = 31 * result + b;
        return result;
    }

My solution looks like this:

Map routesCounted = routes.stream()
            .sorted((r1,r2)-> (int)(r2.lastUpdated - r1.lastUpdated))
            .collect(Collectors.groupingBy(gr -> gr, Collectors.counting()));

Of course casting to int should be replaced with something more appropriated.