Rx list filter. Use this filter to filter list by other list or by internal list

ListByListFilter.java

package com.grasshopper.dialer.util;

import android.support.annotation.NonNull;

import java.util.List;

import rx.Observable;
import rx.functions.Func1;

/**
 * Use this filter to filter list by other list or by internal list
 * @param <T>
 * @param <P>
 */
public class ListByListFilter<T, P> implements Observable.Transformer<List<T>, List<T>> {

    private final Func1<T, List<P>> innerList;
    private final Func1<P, Boolean> filter;

    public ListByListFilter(@NonNull Func1<T, List<P>> innerList, Func1<P, Boolean> filter) {
        this.innerList = innerList;
        this.filter = filter;
    }

    @Override
    public Observable<List<T>> call(Observable<List<T>> source) {
        return source
                .flatMap(Observable::from)
                .filter(forwarding -> {
                    for (P p : innerList.call(forwarding)) {
                        if (filter.call(p)) {
                            return true;
                        }
                    }
                    return false;
                }).toList();
    }
}

observe() .compose(new ListByListFilter<>(CallForwarding::getDestinations, destination -> destination.getNumber().equals(number)));