Question

Can you please explain why my Filtering is not working? (the filter is not done and the message is not printed out).

@Override
protected void fetchValueObjectsListPostSpecificAction() {
    logger.info("~~~size:" + this.valueObjectsList.size());
    // show only scenarios which have applications related defined
    Collections2.filter(this.valueObjectsList, new Predicate<PlanScenarioVo>() {
        @Override
        public boolean apply(final PlanScenarioVo arg0) {
            System.out.println("!!!!!!!!!!---FILTER");
            return (StringUtils.isNotEmpty(arg0.getApplication().getInternalId()));
        }
    });
    logger.info("~~~size POST:" + this.valueObjectsList.size());
}

At least I want to make sure that it gets into the apply method, but I do not see anything on output, only the size(6) and size POST(6).

~~~size:6 
~~~size POST:6

Do you see something wrong with this method?

Thanks,

Answer 1

Collections2.filter returns a filtered Collection, it does not modify the passed collections.

EDIT
As JB Nizmet explains below, Collections2.filter is a view over the original collection, you will see the Predicate evaluated only when you actually iterate over the result or access it.

It will be useful for you to assign the result to a variable, print its size, and look at the stack trace in the predicate method inside a debugger.