To better understand the new stream API I'm trying to convert some old code, but I'm stuck on this one.
public Collection<? extends File> asDestSet() {
HashMap<IFileSourceInfo, Set<File>> map = new HashMap<IFileSourceInfo, Set<File>>();
//...
Set<File> result = new HashSet<File>();
for (Set<File> v : map.values()) {
result.addAll(v);
}
return result;
}
I can't seem to create a valid Collector for it:
public Collection<? extends File> asDestSet() {
HashMap<IFileSourceInfo, Set<File>> map = new HashMap<IFileSourceInfo, Set<File>>();
//...
return map.values().stream().collect(/* what? */);
}
Use flatMap :
return map.values().stream().flatMap(Set::stream).collect(Collectors.toSet());
The flatMap
flattens all of your sets into single stream.
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