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  1. import java.util.HashMap;
  2. import java.util.Map;
  3.  
  4. public final class Main {
  5.  
  6.     private static final Runnable DO_NOTHING = () -> {};
  7.  
  8.     private final Map<Character, Runnable> map;
  9.  
  10.     public Main() {
  11.         map = new HashMap<>();
  12.         map.put('h', () -> moveCursorLeft());
  13.         map.put('j', () -> moveCursorUp());
  14.         map.put('k', () -> moveCursorDown());
  15.         map.put('l', () -> moveCursorRight());
  16.     }
  17.  
  18.     private void handleKeyInput() {
  19.         var c = getPressedKey();
  20.         // Of course, you can pass the method reference to an empty method
  21.         // instead of 'DO_NOTHING'.
  22.         var action = map.getOrDefault(c, DO_NOTHING);
  23.         action.run();
  24.         // In fact, you don't need 'action' and can write:
  25.         //
  26.         // map.getOrDefault(c, DO_NOTHING)
  27.         //     .run();
  28.     }
  29.  
  30.     /**
  31.         Returns the character of the pressed key.
  32.         If no key is pressed, blocks until any key is pressed.
  33.  
  34.         @return
  35.             The character of the pressed key.
  36.     */
  37.     private char getPressedKey() {
  38.         return 'a';
  39.     }
  40.  
  41.     private void moveCursorRight() {}
  42.     private void moveCursorUp() {}
  43.     private void moveCursorDown() {}
  44.     private void moveCursorLeft() {}
  45.  
  46.     public static void main(String[] args) {
  47.         var m = new Main();
  48.         m.handleKeyInput();
  49.     }
  50. }
  51.  
Success #stdin #stdout 0.09s 33660KB
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https://ideone.com/uHjPHl
The Insanity Beyond Null: Null object pattern #3
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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