Dynamic filtering for objects arraylist java

Question

I have such class:

public class FirstTypeMD extends BaseParams {
    Integer framePerSec;

    public FirstTypeMD(Integer energyCons, Integer mass, Integer tempRange, Boolean electricProtect,
            Boolean radioProtect, Integer framePerSec) {
        super(energyCons, mass, tempRange, electricProtect, radioProtect);

        this.framePerSec = framePerSec;
    }


    public void setFramePerSec(Integer framePerSec) {
        this.framePerSec = framePerSec;
    }

    public Integer getFramePerSec() {
        return framePerSec;
    }

}

I would like to create dynamic filter for arraylist with this class objects. For example at certain situation I will need result of filtering by energyCons in another by tempRange and somtimes both of them. I need filter with a lot of variations of this class fields. I also asked such question but here I was suggested to create a lot of constructors for filtering. For me it looks strange :(

Andrew · Accepted Answer · 2020-11-27 10:42:33Z

So, I have created very simple way of arraylist filtering. I used HashMap with predicates:

HashMap<Integer, Predicate<FirstTypeMD>> filter_1 = new HashMap<>();

to which I can add some filters:

switch (p1.getSelectionIndex()) {
case 1: {
sg.filter_1.put(0, model -> model.framePerSec <= 5);
break;
}
case 2: {
sg.filter_1.put(0, model -> model.framePerSec >= 5 & model.framePerSec <= 100);
break;
}
case 3: {
sg.filter_1.put(0, model -> model.framePerSec >= 100);
break;
}
default: {
sg.filter_1.remove(0);
break;
}
}

and then finally I can use this hashmap:

public ArrayList<FirstTypeMD> filterT1() {
        return filter_1.containsKey(0)
                ? new ArrayList<FirstTypeMD>(
                        fTypeArrayList.stream().filter(filter_1.values().stream().reduce(x -> true, Predicate::and))
                                .collect(Collectors.toList()))
                : fTypeArrayList;
    }

and loop over this new array:

for (FirstTypeMD fModeMd : sg.filterT1()) {
                        
}

Maybe my solution isn't so good, but it solved my problem :) Maybe it will be useful for someone else.

P.S. You can also write your suggestions in comments :)

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