---
id: java-recursion
title: "Java Recursion"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["자바 재귀"]
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", "recursion"]
raw_sources: ["https://www.w3schools.com/java/java_recursion.asp"]
applied_in: []
github_commit: ""
---

# [[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):
```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).