CODEWITHSUNDEEP
javalistloopsjava-stream
user2669261
user2669261

Reputation: 416

Java 8: Filter list inside object with another list

I have a list named "foodList" which contains elements of type "Food". The object Food contains a List named "categories" of type "Category".

I am currently implementing a search algorithm to filter food by excluding certain categories.

Excluded Categories are stored inside a List named "excludedCategories".

How can I, using Java 8 and streams, filter the foodList by excluding Food objects whose categoryLists contain any element of the excludedCategories list?

Sample code with loops:

for (Food f: foodList)
{
     for (Category c: f.categories)
     {
          if (excludedCategories.contains(c))
          {
               // REMOVE ITEM FROM foodList
          }
     }
}

Thank you!

Upvotes: 0

Views: 6018

Answers (4)

Michael Mesfin
Michael Mesfin

Reputation: 556

foodList.removeIf(f -> f.getCategories().stream().anyMatch(excludeCategories::contains));

you can use removeIf and anyMatch to achieve the desired result

Upvotes: 0

vivekdubey
vivekdubey

Reputation: 500

you can do like this

    foodList.stream().filter(f -> {
        f.setCats(f.getCats().stream().filter(c -> (!excludedCategories.contains(c))).collect(Collectors.toList()));
        return true;
    }).collect(Collectors.toList()).forEach(System.out::println);

Upvotes: 0

Sunil Dabburi
Sunil Dabburi

Reputation: 1472

Use the stream to filter the excluded categories as following

foodList.stream()
        .filter(f -> f.categories.stream().noneMatch(c -> excludedCategories.contains(c)))
        .collect(Collectors.toList());

Upvotes: 1

GBlodgett
GBlodgett

Reputation: 12819

Streams shouldn't be used to modify the List. Instead you should return a new List with only the appropriate elements in it. You could simply flip the logic a little and use filter:

foodList.stream().flatMap(e -> e.categories.stream())
                 .filter(c -> !excludedCategories.contains(c))
                 .collect(Collectors.toList());

However it would be much simpler to use the built in methods:

foodList.removeIf(e -> !Collections.disjoint(e.categories, excludedCategories));

Collections::disjoint

Collections::removeIf

Upvotes: 5

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