2nd/10_Wiki/Topics/Domain_Programming/Topic_Java/Java_Recursion.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
java-recursion	Java Recursion	Programming_Language	draft	conceptual		자바 재귀		B	0.9	2026-07-04	2026-07-04			java programming w3schools recursion	https://www.w3schools.com/java/java_recursion.asp

Java Recursion

🎯 한 줄 통찰 (One-line insight)

Every recursive method needs an explicit halting condition — its absence produces infinite recursion, the recursive analog of an infinite loop, making the halting condition (e.g., k == 0, end <= start, n <= 1) the single most load-bearing part of any recursive design. [S1]

🧠 핵심 개념 (Core concepts)

• Recursion — a function calling itself to break a complex problem into simpler sub-problems. [S1]
• Halting condition — the required condition where the method stops calling itself, preventing infinite recursion. [S1]
• Call stack unwinding — sum(10) expands to 10 + (9 + (8 + ... + sum(0))), resolving only once the base case returns. [S1]
• Recursion vs. infinite loop danger — like loops, recursion can run forever or exhaust memory if the halting condition is wrong/missing. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Three recursion archetypes shown together — accumulator recursion (sum), side-effecting recursion with no return value (countdown, using void and print-then-recurse), and multiplicative accumulator recursion (factorial) — covering the main shapes recursive functions take. [S1]

📖 세부 내용 (Details)

• Sum 1 to 10: public static int sum(int k) { if (k > 0) { return k + sum(k - 1); } else { return 0; } } ... sum(10); // 55. [S1]
• Sum with start/end: public static int sum(int start, int end) { if (end > start) { return end + sum(start, end - 1); } else { return end; } } ... sum(5, 10); // 45. [S1]
• Countdown (void recursion): static void countdown(int n) { if (n > 0) { System.out.print(n + " "); countdown(n - 1); } } ... countdown(5); // 5 4 3 2 1. [S1]
• Factorial: static int factorial(int n) { if (n > 1) { return n * factorial(n - 1); } else { return 1; } } ... factorial(5); // 120. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 정지 조건의 필수성: 정지 조건이 없으면 무한 재귀에 빠진다는 점이 소스에서 반복 강조됨(반복문의 무한 루프와 동일한 위험). [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 팩토리얼/카운트다운/범위 합계 계산 등 재귀의 대표적 응용 예제들이다. [S1]

💻 코드 패턴 (Code patterns)

Recursive factorial with halting condition (Java):

static int factorial(int n) {
    if (n > 1) {
        return n * factorial(n - 1);
    } else {
        return 1;
    }
}

✅ 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 Methods Return, Java Scope, Java OOP
• 참조 맥락: 함수가 자기 자신을 호출하는 패턴 — 정지 조건 설계가 핵심. OOP 챕터로 이어짐.

📚 출처 (Sources)

• [S1] W3Schools — Java Recursion — https://www.w3schools.com/java/java_recursion.asp

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "Java Recursion" page (Astra wiki-curation, P-Reinforce v3.1 format).