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77 lines
3.8 KiB
Markdown
77 lines
3.8 KiB
Markdown
---
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id: java-recursion
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title: "Java Recursion"
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category: "Programming_Language"
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status: "draft"
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verification_status: "conceptual"
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canonical_id: ""
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aliases: ["자바 재귀"]
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duplicate_of: ""
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source_trust_level: "B"
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confidence_score: 0.9
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created_at: 2026-07-04
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updated_at: 2026-07-04
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review_reason: ""
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merge_history: []
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tags: ["java", "programming", "w3schools", "recursion"]
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raw_sources: ["https://www.w3schools.com/java/java_recursion.asp"]
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applied_in: []
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github_commit: ""
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---
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# [[Java Recursion]]
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## 🎯 한 줄 통찰 (One-line insight)
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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]
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## 🧠 핵심 개념 (Core concepts)
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- **Recursion** — a function calling itself to break a complex problem into simpler sub-problems. [S1]
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- **Halting condition** — the required condition where the method stops calling itself, preventing infinite recursion. [S1]
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- **Call stack unwinding** — `sum(10)` expands to `10 + (9 + (8 + ... + sum(0)))`, resolving only once the base case returns. [S1]
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- **Recursion vs. infinite loop danger** — like loops, recursion can run forever or exhaust memory if the halting condition is wrong/missing. [S1]
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## 🧩 추출된 패턴 (Extracted patterns)
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- **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]
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## 📖 세부 내용 (Details)
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- 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]
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- 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]
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- 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]
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- Factorial: `static int factorial(int n) { if (n > 1) { return n * factorial(n - 1); } else { return 1; } } ... factorial(5); // 120`. [S1]
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## ⚖️ 모순 및 업데이트 (Contradictions & updates)
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- **정지 조건의 필수성**: 정지 조건이 없으면 무한 재귀에 빠진다는 점이 소스에서 반복 강조됨(반복문의 무한 루프와 동일한 위험). [S1]
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## 🛠️ 적용 사례 (Applied in summary)
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현재 발견된 실제 적용 사례가 없습니다 — 팩토리얼/카운트다운/범위 합계 계산 등 재귀의 대표적 응용 예제들이다. [S1]
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## 💻 코드 패턴 (Code patterns)
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Recursive factorial with halting condition (Java):
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```java
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static int factorial(int n) {
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if (n > 1) {
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return n * factorial(n - 1);
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} else {
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return 1;
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}
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}
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```
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## ✅ 검증 상태 및 신뢰도
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- **상태:** draft
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- **검증 단계:** conceptual
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- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
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- **신뢰 점수:** 0.90
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- **중복 검사 결과:** 신규 생성 (New discovery)
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## 🔗 지식 그래프 (Knowledge Graph)
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- **상위/루트:** [[Java Tutorial]]
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- **관련 개념:** [[Java Methods Return]], [[Java Scope]], [[Java OOP]]
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- **참조 맥락:** 함수가 자기 자신을 호출하는 패턴 — 정지 조건 설계가 핵심. OOP 챕터로 이어짐.
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## 📚 출처 (Sources)
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- [S1] W3Schools — Java Recursion — https://www.w3schools.com/java/java_recursion.asp
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## 📝 변경 이력 (Change history)
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- 2026-07-04: Initial draft synthesized from the W3Schools "Java Recursion" page (Astra wiki-curation, P-Reinforce v3.1 format).
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