StreamTest.java

public class StreamTest {

    @Test
    public static void test () {

        final List<Integer> list = new ArrayList<>();
        list.add(1);
        list.add(2);
        list.add(3);

        final Stream<Integer> stream = list.stream().filter(a -> a > 2);

        list.add(4);
        stream.forEach(System.out::print);
    }

}

Результат

[TestNG] Running:
  
34
===============================================
Default Suite
Total tests run: 1, Failures: 0, Skips: 0
===============================================