JavaFilterOperation

JavaFilterOperation.java

public class JavaFilterOperation {

    private List<String> items;

    @FunctionalInterface
    interface FilterOperation {
        Boolean filter(String element);
    }

    private List<String> filterBy(FilterOperation fn) {
        return items.stream()
                .filter(fn::filter) // applying the function
                .collect(Collectors.toList());
    }

    public void doFilter() {
        filterBy((element) -> {
            return element.length() > 0;
            // calling the function with an actual lambda
        });
    }
}