Java Coding Problems

180. Filtering the non-zero elements of a stream

In Chapter 8, Functional Style Programming – Fundamentals and Design Patterns, in the Writing functional interfaces section, we defined a filter() method based on a functional interface named Predicate. The Java Stream API already has such a method, and the functional interface is called java.util.function.Predicate.

Let's assume that we have the following List of integers:

List<Integer> ints = Arrays.asList(1, 2, -4, 0, 2, 0, -1, 14, 0, -1);

Streaming this list and extracting only non-zero elements can be accomplished as follows:

List<Integer> result = ints.stream()  .filter(i -> i != 0)  .collect(Collectors.toList());

The resulting list will contain the following elements: 1, 2, -4, 2, -1, ...