How to filter nested streams in Java 8 with lambda productions

Question

I am trying to filter my Deals based on my Deal options but when I try to filter the code I get a type mismatch error that Set<DealOptions> cannot be converted to boolean. I want to keep the deals when all the deal options are red.

Here is my code:

import java.util.*;
import java.util.stream.Collectors;

class Deal {
    String dealname;
    String dealprice;
    Set<DealOptions> dealop;

    public String getDealname() {
        return dealname;
    }

    public void setDealname(String dealname) {
        this.dealname = dealname;
    }

    public String getDealprice() {
        return dealprice;
    }

    public void setDealprice(String dealprice) {
        this.dealprice = dealprice;
    }

    public Set<DealOptions> getDealop() {
        return dealop;
    }

    public void setDealop(Set<DealOptions> dealop) {
        this.dealop = dealop;
    }

}

class DealOptions {
    String optname;
    String color;

    public String getOptname() {
        return optname;
    }

    public void setOptname(String optname) {
        this.optname = optname;
    }

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

}

public class Test {

    public static void main(String[] args) 
             {

        Deal s = new Deal();
        Set<DealOptions> ops = new HashSet<DealOptions>();
        DealOptions op = new DealOptions();
        s.setDealname("mongo");
        s.setDealprice("500");

        op = new DealOptions();
        op.setColor("red");
        op.setOptname("redop");

        ops.add(op);
        op = new DealOptions();
        op.setColor("blue");
        op.setOptname("blueop");

        ops.add(op);
        op = new DealOptions();
        op.setColor("green");
        op.setOptname("greenop");

        ops.add(op);

        s.setDealop(ops);

        List<Deal> dl = new ArrayList<Deal>();

        dl.add(s);
        ops = new HashSet<DealOptions>();
        s = new Deal();
        op = new DealOptions();
        s.setDealname("test2");
        s.setDealprice("200");

        op = new DealOptions();
        op.setColor("indigo");
        op.setOptname("indigop");

        ops.add(op);
        op = new DealOptions();
        op.setColor("violet");
        op.setOptname("violetop");

        ops.add(op);
        op = new DealOptions();
        op.setColor("orange");
        op.setOptname("orangeop");

        ops.add(op);

        s.setDealop(ops);

        dl.add(s);

        List<Deal> dev = dl.stream().filter(
                (p) -> p.getDealop().stream().filter((po) -> po.getColor().equals("red")).collect(Collectors.toSet()))
                .collect(Collectors.toList()); // error here

    }
}

Error:

Cannot convert from Set to boolean

How do rectify this error how can I filter my deals based on my deal options?

Solution

You can use allMatch(predicate) to determine if all deals of an option are red:

Returns whether all elements of this stream match the provided predicate.

In this case, the predicate simply tells whether an option is red or not.

List<Deal> output =
    dl.stream()
      .filter(d -> d.getDealop().stream().allMatch(po -> po.getColor().equals("red")))
      .collect(Collectors.toList());

Comments

[Mam's]

List<Deal> dd1 = dl.stream().filter(d->d.getDealop().stream().anyMatch(p->p.g‌​etColor().equals("re‌​d"))) .collect(Collectors.toList());

[Ram]

I think this list would return empty, if the list contains any other color rather than "red" color. cause it would return false as "Returns whether all elements of this stream match the provided predicate." anyMatch returns all in this case.