What is the best way to filter a Java Collection?

Question

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

Answer 1

Wait for Java 8:

List olderThan30 = 
  //Create a Stream from the personList
  personList.stream().
  //filter the element to select only those with age >= 30
  filter(p -> p.age >= 30).
  //put those filtered elements into a new List.
  collect(Collectors.toList());