docs(10_Wiki): Dev 폴더 누락분 반영 — Topic_Programming으로 통합

이전 재구성 작업에서 Dev/ 폴더가 누락되었던 것을 반영. - Dev/Topic_Programming(중첩 폴더, 78개)은 Dev 자체 최상위 폴더들 (Architecture/Conventions/Engineering_Intelligence 등)과 완전 중복이라 제거. - Dev 최상위 엔지니어링 지식 폴더(Architecture/Conventions/Engineering_Intelligence/ Failure_Library/Generalized_Principles/Language/Pattern_Catalog/Platform_Guides/ Subsystems, 77개)는 이미 Topic_Programming/Topic_Programming에 더 최신 버전이 존재해 중복 제거(고유 콘텐츠 1개는 예외 처리하여 이동 보존). - Dev의 W3Schools 언어 튜토리얼 폴더(Topic_C/CPP/CSS/CSharp/HOWTO/HTML/Java/ JavaScript/PHP/Python/SQL/W3CSS, 1201개)는 전부 Topic_Programming 하위로 이동. - 에이전트 운영 상태(.astra/docs)는 그대로 유지, 콘텐츠 폴더만 정리. - Topic_Programming 최종 문서 수: 2784 → 3985.
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+---
+id: java-hashset
+title: "Java HashSet"
+category: "Programming_Language"
+status: "draft"
+verification_status: "conceptual"
+canonical_id: ""
+aliases: ["자바 HashSet"]
+duplicate_of: ""
+source_trust_level: "B"
+confidence_score: 0.9
+created_at: 2026-07-04
+updated_at: 2026-07-04
+review_reason: ""
+merge_history: []
+tags: ["java", "programming", "w3schools", "collections-framework", "hashset"]
+raw_sources: ["https://www.w3schools.com/java/java_hashset.asp"]
+applied_in: []
+github_commit: ""
+---
+
+# [[Java HashSet]]
+
+## 🎯 한 줄 통찰 (One-line insight)
+Checking `numbers.contains(i)` for every value 1-10 against a HashSet with only {4, 7, 8} added demonstrates that HashSet's real strength is O(1)-style membership testing across a range — this "presence check across a range" pattern is a distinctly Set-shaped use case that ArrayList's linear `contains()` scan doesn't showcase as naturally. [S1]
+
+## 🧠 핵심 개념 (Core concepts)
+- **`HashSet`** — a Set implementation where every element is unique; implements the `Set` interface. [S1]
+- **Duplicate handling** — adding an already-present element is silently a no-op (no error, no duplicate). [S1]
+- **`contains()`** — membership test. [S1]
+- **Wrapper classes for primitives** — same rule as ArrayList: `Integer` for int, etc. [S1]
+- **`var` keyword and Set-typed variable** — same patterns as List (`var cars = new HashSet<String>();`, `Set<String> cars = new HashSet<>();`). [S1]
+
+## 📖 세부 내용 (Details)
+- Duplicate ignored: `cars.add("BMW"); cars.add("BMW"); // only appears once`. [S1]
+- Membership test across a range: `HashSet<Integer> numbers = new HashSet<Integer>(); numbers.add(4); numbers.add(7); numbers.add(8); for (int i = 1; i <= 10; i++) { if (numbers.contains(i)) { System.out.println(i + " was found in the set."); } else {...} }`. [S1]
+
+## ⚖️ 모순 및 업데이트 (Contradictions & updates)
+소스에서 모순되는 정보는 발견되지 않음.
+
+## 🛠️ 적용 사례 (Applied in summary)
+현재 발견된 실제 적용 사례가 없습니다 — 1~10 범위 내 값의 존재 여부를 검사하는 예제가 HashSet의 빠른 조회 특성을 보여주는 대표 사례다. [S1]
+
+## 💻 코드 패턴 (Code patterns)
+Fast membership check across a range with HashSet (Java):
+```java
+HashSet<Integer> numbers = new HashSet<Integer>();
+numbers.add(4);
+numbers.add(7);
+numbers.add(8);
+for (int i = 1; i <= 10; i++) {
+    if (numbers.contains(i)) {
+        System.out.println(i + " was found in the set.");
+    } else {
+        System.out.println(i + " was not found in the set.");
+    }
+}
+```
+
+## ✅ 검증 상태 및 신뢰도
+- **상태:** draft
+- **검증 단계:** conceptual
+- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
+- **신뢰 점수:** 0.90
+- **중복 검사 결과:** 신규 생성 (New discovery)
+
+## 🔗 지식 그래프 (Knowledge Graph)
+- **상위/루트:** [[Java Tutorial]]
+- **관련 개념:** [[Java Set]], [[Java TreeSet]], [[Java LinkedHashSet]], [[Java ArrayList]]
+- **참조 맥락:** Set의 대표 구현체 — 정렬된 TreeSet 챕터로 이어짐.
+
+## 📚 출처 (Sources)
+- [S1] W3Schools — Java HashSet — https://www.w3schools.com/java/java_hashset.asp
+
+## 📝 변경 이력 (Change history)
+- 2026-07-04: Initial draft synthesized from the W3Schools "Java HashSet" page (Astra wiki-curation, P-Reinforce v3.1 format).