Reducing Predicates in Java

Question

I have been trying to adapt this approach to reduce my predicates into one filter.

Class definition:

@Command(name = "Devices", description = "Fetch Devices from SecureTrack", subcommands = {InterfaceCommand.class})
class TufinDevices implements Runnable {
.
.
.
private void filter(TufinDeviceCollection<TufinDevice> devices) {
List<Predicate<? super TufinDevice>> filters = new ArrayList();

if (modelContains != null) {

        System.out.println("modelContains " + Arrays.asList(deviceID));
        Predicate< ? super TufinDevice> deviceFilter = device -> Arrays.stream(modelContains)
                .allMatch(input -> device.getModel().toLowerCase().contains(input.toLowerCase()));

        filters.add(deviceFilter);

    }

if (hostNameContains != null) {
        Predicate<TufinDevice> deviceFilter = device -> Arrays.stream(hostNameContains)
                .allMatch(input -> device.getHostName().toLowerCase().contains(input.toLowerCase()));

        filters.add(deviceFilter);
    }
 devices.stream().filter(filters.stream().reduce(Predicate::or).orElse(t->true));
 }

I do not understand how this line of code is supposed to work.

devices.stream().filter(filters.stream().reduce(Predicate::or).orElse(t->true));

How does that line need to be implemented in order to work. Its complaining that

Predicate<CAP1> can't be converted to Predicate<? super CAP2>

The code is contained in a method, within a class. I will update with both. — CoupFlu, Sep 17 '19 at 19:51
Its complicated because it is a Picocli project. I'll post the line though. — CoupFlu, Sep 17 '19 at 20:01
OK, I see the problem now. The compiler can't tell whether your `deviceFilter` inside the first `if` block matches the type of `filters`. I would recommend declaring `deviceFilter` as `Predicate`, instead of `Predicate super TufinDevice>`. — Dawood ibn Kareem, Sep 17 '19 at 20:08
Ok, that did it, but in the future how can i pass something that possible extends TufinDevice? — CoupFlu, Sep 17 '19 at 20:11

Reducing Predicates in Java

0 Answers0