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  1. import java.util.HashMap;
  2. import java.util.Map;
  3.  
  4. public final class Main {
  5.  
  6.     private final Map<Character, Runnable> map;
  7.  
  8.     public Main() {
  9.         map = new HashMap<>();
  10.         map.put('h', () -> moveCursorLeft());
  11.         map.put('j', () -> moveCursorUp());
  12.         map.put('k', () -> moveCursorDown());
  13.         map.put('l', () -> moveCursorRight());
  14.     }
  15.  
  16.     public void handleKeyInput() {
  17.         var c = getPressedKey();
  18.         var action = map.get(c);
  19.         if (action == null) {
  20.             // Does nothing with keys not associated with actions.
  21.             return;
  22.         }
  23.         action.run();
  24.     }
  25.  
  26.     /**
  27.         Returns the character of the pressed key.
  28.         If no key is pressed, blocks until any key is pressed.
  29.  
  30.         @return
  31.             The character of the pressed key.
  32.     */
  33.     private char getPressedKey() {
  34.         return 'a';
  35.     }
  36.  
  37.     private void moveCursorRight() {}
  38.     private void moveCursorUp() {}
  39.     private void moveCursorDown() {}
  40.     private void moveCursorLeft() {}
  41.  
  42.     public static void main(String[] args) {
  43.         var m = new Main();
  44.         m.handleKeyInput();
  45.     }
  46. }
  47.  
Success #stdin #stdout 0.06s 33084KB
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https://ideone.com/HnA7eL
The Insanity Beyond Null: Null object pattern #2
language:
Java (HotSpot 12)
created:
3 years ago
visibility:
public

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