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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 Ideone {
  9.  
  10.     private static final Map<Class<?>, List<Object>> 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.         String stringOne = "stringOne";
  27.         add(stringOne);
  28.  
  29.         String stringTwo = "stringTwo";
  30.         add(stringTwo);
  31.  
  32.         List<SomeEnemy> fetchOne = getAll(SomeEnemy.class);
  33.         SomeEnemy firstFetched = fetchOne.get(0);
  34.         fetchOne.add(new SomeEnemy());
  35.         System.out.println(firstFetched == firstSomeEnemy);
  36.  
  37.         remove(firstFetched);
  38.         List<SomeEnemy> fetchTwo = getAll(SomeEnemy.class);
  39.         SomeEnemy secondFetched = fetchTwo.get(0);
  40.         System.out.println(secondFetched == secondSomeEnemy);
  41.  
  42.         remove(secondSomeEnemy);
  43.         List<SomeEnemy> fetchThree = getAll(SomeEnemy.class);
  44.         System.out.println(fetchThree.isEmpty());
  45.  
  46.         List<AnotherEnemy> fetchFour = getAll(AnotherEnemy.class);
  47.         AnotherEnemy fourthFetched = fetchFour.get(0);
  48.         System.out.println(fourthFetched == firstAnotherEnemy);
  49.  
  50.         remove(firstAnotherEnemy);
  51.         List<AnotherEnemy> fetchFive = getAll(AnotherEnemy.class);
  52.         AnotherEnemy fifthFetched = fetchFive.get(0);
  53.         System.out.println(fifthFetched == secondAnotherEnemy);
  54.  
  55.         remove(secondAnotherEnemy);
  56.         List<AnotherEnemy> fetchSix = getAll(AnotherEnemy.class);
  57.         System.out.println(fetchSix.isEmpty());
  58.  
  59.         List<String> fetchSeven = getAll(String.class);
  60.         String seventFetched = fetchSeven.get(0);
  61.         System.out.println(seventFetched.equals(stringOne));
  62.  
  63.         remove(stringOne);
  64.         List<String> fetchEight = getAll(String.class);
  65.         String eightFetched = fetchEight.get(0);
  66.         System.out.println(eightFetched.equals(stringTwo));
  67.  
  68.         remove(stringTwo);
  69.         List<String> ninthFetch = getAll(String.class);
  70.         System.out.println(ninthFetch.isEmpty());
  71.     }
  72.  
  73.     static void add(Object entity) {
  74.         Class<?> type = entity.getClass();
  75.  
  76.         if (!entities.containsKey(type)) {
  77.             entities.put(type, new CopyOnWriteArrayList<>());
  78.         }
  79.  
  80.         entities.get(type).add(entity);
  81.     }
  82.  
  83.     private static <T> List<T> getAll(Class<? extends T> type) {
  84.         return new ArrayList<>(getListCasted(type));
  85.     }
  86.  
  87.     @SuppressWarnings("unchecked")
  88.     private static <T> List<T> getListCasted(Class<? extends T> type) {
  89.         return (List<T>) entities.getOrDefault(type, Collections.emptyList());
  90.     }
  91.  
  92.     public static void remove(Object entity) {
  93.         getListCasted(entity.getClass()).remove(entity);
  94.     }
  95. }
  96.  
  97. interface Entity {}
  98. interface Enemy extends Entity {}
  99.  
  100. class SomeEnemy implements Enemy {}
  101. class AnotherEnemy implements Enemy {}
Success #stdin #stdout 0.06s 32456KB
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https://ideone.com/EWMJbI
language:
Java (HotSpot 12)
created:
4 years ago
visibility:
public

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