Niraj Sonawane :
I need to remove all empty/null values from List<Optional<String>>.
Example:
List<Optional<String>> list = new ArrayList<>();
list.add(Optional.empty());
list.add(Optional.of("Str1"));
list.add(Optional.of("Str2"));
list.add(Optional.of("Str3"));
list.add(Optional.of("Str4"));
list.add(Optional.of("Str5"));
list.add(Optional.empty());
list.add(Optional.ofNullable(null));
Currently, I'm using one of the below approaches:
Way 1:
List<String> collect = list.stream()
.filter(Optional::isPresent)
.map(obj ->obj.get())
.collect(Collectors.toList());
Way 2:
List<Optional<String>> emptlist = new ArrayList<>();
emptlist.add(Optional.empty());
list.removeAll(emptlist);
Is there any other better way?
Naman :
With Java9, you can do this using the newly added Optional::stream API :
List<String> collect = list.stream()
.flatMap(Optional::stream)
.collect(Collectors.toList());
This method can be used to transform a
Streamof optional elements to aStreamof present value elements.
Sticking with Java8, the Way1 in the question is good enough IMHO -
List<String> collect = list.stream()
.filter(Optional::isPresent)
.map(Optional::get) // just a small update of using reference
.collect(Collectors.toList());
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