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javacollectionsfilter

How to filter a Java Collection (based on predicate)?

I want to filter a java.util.Collection based on a predicate.

Solution

  • Java 8 (2014) solves this problem using streams and lambdas in one line of code:

    List<Person> beerDrinkers = persons.stream()
    .filter(p -> p.getAge() > 16).collect(Collectors.toList());

    Here's a tutorial.

    Use Collection#removeIf to modify the collection in place. (Notice: In this case, the predicate will remove objects who satisfy the predicate):

    persons.removeIf(p -> p.getAge() <= 16);

    lambdaj allows filtering collections without writing loops or inner classes:

    List<Person> beerDrinkers = select(persons, having(on(Person.class).getAge(),
    greaterThan(16)));

    Can you imagine something more readable?

    Disclaimer: I am a contributor on lambdaj