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  1. import java.util.List;
  2. import java.util.Map;
  3. import java.util.Optional;
  4. import java.util.stream.Collectors;
  5. import static java.util.Map.entry;
  6.  
  7. public final class Main {
  8.  
  9.     private static final Map<String, Runnable> COMMAND_MAP = Map.ofEntries(
  10.             entry("help", () -> printHelp()),
  11.             entry("quit", () -> exitProgram()),
  12.             entry("shutdown", () -> shutdownSystem()));
  13.  
  14.     private static void printHelp() {
  15.         System.out.println("printHelp");
  16.     }
  17.  
  18.     private static void exitProgram() {
  19.         System.out.println("exitProgram");
  20.     }
  21.  
  22.     private static void shutdownSystem() {
  23.         System.out.println("shutdownSystem");
  24.     }
  25.  
  26.     private static List<String> getCommandList() {
  27.         return List.of("help", "reboot", "shutdown");
  28.     }
  29.  
  30.     private static void fixMe() {
  31.         var list = getCommandList().stream()
  32.             .flatMap(n -> Optional.ofNullable(COMMAND_MAP.get(n)).stream())
  33.             .collect(Collectors.toList());
  34.  
  35.         // The next is also fine, but the number of elements differs:
  36.         //
  37.         // var list = getCommandList().stream()
  38. 		//     .map(n -> COMMAND_MAP.getOrDefault(n, () -> {}))
  39.         //     .collect(Collectors.toList());
  40.  
  41.         list.forEach(r -> r.run());
  42.     }
  43.  
  44.     public static void main(String[] args) {
  45.         fixMe();
  46.     }
  47. }
  48.  
Success #stdin #stdout 0.08s 34372KB
comments (?)
stdin 
Standard input is empty
stdout 
printHelp
shutdownSystem
https://ideone.com/K86qGn
The Insanity Beyond Null: Exercise 2 (Java) [sample fix]
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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