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  1. import java.util.ArrayList;
  2. import java.util.Collections;
  3. import java.util.HashMap;
  4. import java.util.List;
  5. import java.util.Map;
  6. import java.util.concurrent.CopyOnWriteArrayList;
  7.  
  8. class Scratch {
  9.  
  10.     private static final Map<Class<? extends Entity>, List<Entity>> entities
  11.         = new HashMap<>();
  12.  
  13.     public static void main(String[] args) {
  14.         SomeEnemy firstSomeEnemy = new SomeEnemy();
  15.         add(firstSomeEnemy);
  16.  
  17.         SomeEnemy secondSomeEnemy = new SomeEnemy();
  18.         add(secondSomeEnemy);
  19.  
  20.         AnotherEnemy firstAnotherEnemy = new AnotherEnemy();
  21.         add(firstAnotherEnemy);
  22.  
  23.         AnotherEnemy secondAnotherEnemy = new AnotherEnemy();
  24.         add(secondAnotherEnemy);
  25.  
  26.         List<SomeEnemy> fetchOne = getAll(SomeEnemy.class);
  27.         SomeEnemy firstFetched = fetchOne.get(0);
  28.         fetchOne.add(new SomeEnemy());
  29.         System.out.println(firstFetched == firstSomeEnemy);
  30.  
  31.         remove(firstFetched);
  32.         List<SomeEnemy> fetchTwo = getAll(SomeEnemy.class);
  33.         SomeEnemy secondFetched = fetchTwo.get(0);
  34.         System.out.println(secondFetched == secondSomeEnemy);
  35.  
  36.         remove(secondSomeEnemy);
  37.         List<SomeEnemy> fetchThree = getAll(SomeEnemy.class);
  38.         System.out.println(fetchThree.isEmpty());
  39.  
  40.         List<AnotherEnemy> fetchFour = getAll(AnotherEnemy.class);
  41.         AnotherEnemy fourthFetched = fetchFour.get(0);
  42.         System.out.println(fourthFetched == firstAnotherEnemy);
  43.  
  44.         remove(firstAnotherEnemy);
  45.         List<AnotherEnemy> fetchFive = getAll(AnotherEnemy.class);
  46.         AnotherEnemy fifthFetched = fetchFive.get(0);
  47.         System.out.println(fifthFetched == secondAnotherEnemy);
  48.  
  49.         remove(secondAnotherEnemy);
  50.         List<AnotherEnemy> fetchSix = getAll(AnotherEnemy.class);
  51.         System.out.println(fetchSix.isEmpty());
  52.  
  53.     }
  54.  
  55.     static void add(Entity entity) {
  56.         Class<? extends Entity> type = entity.getClass();
  57.  
  58.         if (!entities.containsKey(type)) {
  59.             entities.put(type, new CopyOnWriteArrayList<>());
  60.         }
  61.  
  62.         entities.get(type).add(entity);
  63.     }
  64.  
  65.     private static <T extends Entity> List<T> getAll(Class<? extends T> type) {
  66.         return new ArrayList<>(getListCasted(type));
  67.     }
  68.  
  69.     @SuppressWarnings("unchecked")
  70.     private static <T extends Entity> List<T> getListCasted(Class<? extends T> type) {
  71.         return (List<T>) entities.getOrDefault(type, Collections.emptyList());
  72.     }
  73.  
  74.     public static void remove(Entity entity) {
  75.         getListCasted(entity.getClass()).remove(entity);
  76.     }
  77. }
  78.  
  79. interface Entity {}
  80. interface Enemy extends Entity {}
  81.  
  82. class SomeEnemy implements Enemy {}
  83. class AnotherEnemy implements Enemy {}
Success #stdin #stdout 0.06s 32400KB
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https://ideone.com/KArSaY
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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