1. import java.util.Collection;
  2. import java.util.HashSet;
  3. import java.util.Set;
  4. import java.util.concurrent.ConcurrentHashMap;
  5. import java.util.concurrent.Executors;
  6. import java.util.concurrent.ScheduledExecutorService;
  7. import java.util.concurrent.TimeUnit;
  8. import java.util.logging.Logger;
  10. public class CollectionWatcher {
  12. private final Logger logger = Logger.getLogger(CollectionWatcher.class.getName());
  13. private final ConcurrentHashMap<Collection<?>, Object> collectionStates = new ConcurrentHashMap<>(); // Stores collection states
  14. private final Set<Collection<?>> watchedCollections = new HashSet<>(); // Keeps track of watched collections
  15. private final ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor();
  16. private final long checkIntervalMillis;
  18. public CollectionWatcher(long checkIntervalMillis) {
  19. this.checkIntervalMillis = checkIntervalMillis;
  20. }
  22. public void watchCollection(Collection<?> collection) {
  23. if (collection == null) {
  24. logger.severe("Cannot watch a null collection.");
  25. return;
  26. }
  27. watchedCollections.add(collection);
  28. collectionStates.put(collection, collection); // Initial state
  29. }
  31. public void stopWatching() {
  32. scheduler.shutdown();
  33. }
  35. public void startWatching() {
  36. scheduler.scheduleAtFixedRate(this::checkCollections, 0, checkIntervalMillis, TimeUnit.MILLISECONDS);
  37. }
  39. private void checkCollections() {
  40. for (Collection<?> collection : watchedCollections) {
  41. try {
  42. Collection<?> currentCollection = collectionStates.get(collection);
  43. if (currentCollection == null) {
  44. logger.warning("Collection " + collection + " not found. Possibly removed.");
  45. continue;
  46. }
  48. if (!collection.equals(currentCollection)) {
  49. logger.info("Collection " + collection + " changed.");
  50. collectionStates.put(collection, collection); // Update the state
  51. }
  52. } catch (Exception e) {
  53. logger.severe("Error checking collection " + collection + ": " + e.getMessage());
  54. }
  55. }
  56. }
  58. public static void main(String[] args) throws InterruptedException {
  59. CollectionWatcher watcher = new CollectionWatcher(1000); // Check every 1 second
  61. // Example Usage
  62. Collection<String> collection1 = new HashSet<>();
  63. collection1.add("item1");
  64. watcher.watchCollection(collection1);
  66. Collection<Integer> collection2 = new HashSet<>();
  67. collection2.add(1);
  68. collection2.add(2);
  69. watcher.watchCollection(collection2);
  72. watcher.startWatching();
  74. Thread.sleep(5000); // Run for 5 seconds
  76. watcher.stopWatching();
  77. }
  78. }

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