java-fundamentals

SKILL.md

This skill covers Java fundamentals including syntax, OOP, collections, streams API, and exception handling for Java 8-21.

| Indexed access | ArrayList | O(1) random access | | Unique elements | HashSet | O(1) contains | | Sorted unique | TreeSet | O(log n) sorted | | Key-value pairs | HashMap | O(1) get/put |

| NullPointerException | Null reference | Use Optional | | ConcurrentModificationException | Modify during iteration | Iterator.remove() | | ClassCastException | Wrong type | Use generics |

掌握核心 Java 編程 - 語法、OOP、集合、流和異常處理 來源：pluginagentmarketplace/custom-plugin-java。

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