Java 8 Stream String Null Or Empty Filter

Question

I\'ve got Google Guava inside Stream:

this.map.entrySet().stream()
.filter(entity -> !Strings.isNullOrEmpty(entity.getValue()))
.map(obj -> String.form         


        

Answer 1

You can break down the filter into two steps:

this.map.entrySet().stream()
    .filter(entity -> entity.getValue() != null)
    .filter(entity -> !entity.getValue().isEmpty())
    .map(obj -> String.format("%s=%s", obj.getKey(), obj.getValue()))
    .collect(Collectors.joining(","))

On a side note, most Map.Entry.toString() implementations do exactly what you're doing in map(), so you could theoretically just do map(Map.Entry::toString). But I wouldn't rely on that unless you're producing a toString() or something that doesn't require documented or deterministic behavior.

Also, I know you want to abandon Guava, but here's a solution that might make you reconsider:

Joiner.on(',').withKeyValueSeparator("=")
      .join(Maps.filterValues(map, Predicates.not(Strings::isNullOrEmpty)));