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  1. import java.util.List;
  2. import java.util.function.Predicate;
  3. import java.util.stream.Collectors;
  4.  
  5. public final class Main {
  6.  
  7.     public static void main(String[] args) {
  8.         Predicate<String> p = s -> s.startsWith("b");
  9.         findFirst(p);
  10.         limitList(p);
  11.     }
  12.  
  13.     public static void findFirst(Predicate<String> matchesFavorite) {
  14.         var firstFavorite = List.of("foo", "bar", "baz")
  15.             .stream()
  16.             .filter(matchesFavorite)
  17.             .findFirst();
  18.         firstFavorite.ifPresent(s -> System.out.println("A:" + s));
  19.  
  20.         // As a result, it is equivalent to the following code:
  21.         List.of("foo", "bar", "baz")
  22.             .stream()
  23.             .filter(matchesFavorite)
  24.             .findFirst()
  25.             .ifPresent(s -> System.out.println("B:" + s));
  26.     }
  27.  
  28.     public static void limitList(Predicate<String> matchesFavorite) {
  29.         var favoriteList = List.of("foo", "bar", "baz")
  30.             .stream()
  31.             .filter(matchesFavorite)
  32.             .limit(1)
  33.             .collect(Collectors.toList());
  34.  
  35.         favoriteList.forEach(s -> System.out.println("C:" + s));
  36.  
  37.         // Or
  38.         for (var s : favoriteList) {
  39.             // This loop only runs once at most.
  40.             System.out.println("D:" + s);
  41.         }
  42.  
  43.         // Or again, it could be as follows, but...
  44.         if (favoriteList.size() != 0) {
  45.             var s = favoriteList.get(0);
  46.             System.out.println("E:" + s);
  47.         }
  48.  
  49.         // As a result, it is equivalent to the following code:
  50.         List.of("foo", "bar", "baz")
  51.             .stream()
  52.             .filter(matchesFavorite)
  53.             .limit(1)
  54.             .forEach(s -> System.out.println("F:" + s));
  55.     }
  56. }
  57.  
Success #stdin #stdout 0.1s 36696KB
comments (?)
stdin
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Standard input is empty
stdout
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A:bar
B:bar
C:bar
D:bar
E:bar
F:bar
https://ideone.com/NzUvcK
The Insanity Beyond Null: Null object pattern #7
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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