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  1. import java.util.Arrays;
  2. import java.util.List;
  3. import java.util.Optional;
  4. import java.util.function.Function;
  5. import java.util.stream.Collectors;
  6.  
  7. public final class Main {
  8.  
  9. 	private static <T, U> List<U> compactMap(
  10. 			List<T> list,
  11. 			Function<T, Optional<U>> transform) {
  12. 	    return list.stream()
  13. 	        .map(e -> transform.apply(e))
  14. 	        .flatMap(o -> o.stream())
  15. 	        .collect(Collectors.toList());
  16. 	}
  17.  
  18.     public static void main(String[] args) {
  19.     	var list = Arrays.asList(
  20.     		"The", "quick", "brown", null, "jumps",
  21.     		"over", "the", "lazy", null);
  22.     	var all = compactMap(
  23.     		list,
  24.     		e -> Optional.ofNullable(e)
  25.     			.map(s -> Integer.valueOf(s.length())));
  26.     	for (var e : all) {
  27.     		System.out.println(e);
  28.     	}
  29.     }
  30. }
  31.  
Success #stdin #stdout 0.09s 33888KB
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https://ideone.com/xRs9sK
The Insanity Beyond Null: compactMap
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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