is there a Java equivalent to Javascript's “some” method?

Question

I have a collection and I would like to know if at least one element meets some condition. Essentially, what some does in JavaScript, I would like to do on a collection!

Answer 1

You can use CollectionUtils from Apache commons-collections:

List primes = Arrays.asList(3, 5, 7, 11, 13)
CollectionUtils.exists(primes, even);  //false

Where even is a predicate:

Predicate even = new Predicate() {
    public boolean evaluate(Object object) {
        return ((Integer)object) % 2 == 0;
    }
}

Or in an inlined version:

List primes = Arrays.asList(2, 3, 5, 7, 11, 13)
CollectionUtils.exists(primes, new Predicate() {
    public boolean evaluate(Object object) {
        return ((Integer)object) % 2 == 0;
    }
});

Yes, it is ugly for two reasons:

1. Java does not (yet) support functions as first-class citizens, which are emulated with Single-Abstract-Method interface.
2. commons-collections does not support generics.

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On the other hand in modern JVM languages like Scala you can write:

List(3,5,7,11,13,17).exists(_ % 2 == 0)