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  1. import java.util.Arrays;
  2. import java.util.Collections;
  3. import java.util.List;
  4. import java.util.stream.Collectors;
  5.  
  6. public final class Main {
  7.  
  8.     public static final class Node {
  9.  
  10.         private final String name;
  11.         private final List<Node> children;
  12.  
  13.         public Node(String name) {
  14.             this(name, Collections.emptyList());
  15.         }
  16.  
  17.         public Node(String name, String... children) {
  18.             this(name, Arrays.stream(children)
  19.                 .map(Node::new)
  20.                 .collect(Collectors.toUnmodifiableList()));
  21.         }
  22.  
  23.         private Node(String name, List<Node> list) {
  24.             this.name = name;
  25.             this.children = list;
  26.         }
  27.  
  28.         public List<Node> getChildNodes() {
  29.             return children;
  30.         }
  31.  
  32.         @Override
  33.         public String toString() {
  34.             return "name: " + name;
  35.         }
  36.     }
  37.  
  38.     private static List<Node> getNodes() {
  39.         return List.of(
  40.             new Node("image", "raw", "jpeg", "png"),
  41.             new Node("video", "mp4"),
  42.             new Node("game"),
  43.             new Node("music", "wav", "mp3"));
  44.     }
  45.  
  46.     private static void fixMe() {
  47.         var list = getNodes().stream()
  48.             .map(n -> n.getChildNodes().stream().findFirst().orElse(null))
  49.             // The next statement is equivalent to '.filter(Objects::nonNull)'
  50.             .filter(n -> n != null)
  51.             .collect(Collectors.toList());
  52.         list.forEach(System.out::println);
  53.     }
  54.  
  55.     public static void main(String[] args) {
  56.         fixMe();
  57.     }
  58. }
  59.  
Success #stdin #stdout 0.11s 36580KB
comments (?)
stdin
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Standard input is empty
stdout
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name: raw
name: mp4
name: wav
https://ideone.com/KgetT1
The Insanity Beyond Null: Exercise 1 (Java)
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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