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-arrays-multi
title: "Java Arrays Multi"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["multidimensional arrays", "자바 다차원 배열"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.88
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["java", "programming", "w3schools", "arrays", "multidimensional"]
raw_sources: ["https://www.w3schools.com/java/java_arrays_multi.asp"]
applied_in: []
github_commit: ""
---
# [[Java Arrays Multi]]
## 🎯 한 줄 통찰 (One-line insight)
Java's 2D arrays are actually "arrays of arrays," not a fixed grid — each row can have a different length (a "jagged array"), which the source proves by showing `myNumbers[0].length` (3) differing from `myNumbers[1].length` (5) in the same array. [S1]
## 🧠 핵심 개념 (Core concepts)
- **2D array literal** — `int[][] myNumbers = { {1, 4, 2}, {3, 6, 8} };` — each inner `{}` is one row. [S1]
- **Two-index access** — `myNumbers[row][col]`; row index first, then column. [S1]
- **Element mutation** — `myNumbers[1][2] = 9;` overwrites via the same two-index notation. [S1]
- **`.length` for rows, `[row].length` for columns** — the outer array's length is row count; each row array has its own independent length. [S1]
- **Jagged arrays are valid** — rows may have different lengths in Java. [S1]
- **Nested loop traversal** — indexed double for-loop, or double for-each (`for (int[] row : myNumbers) { for (int num : row) {...} }`). [S1]
## 🧩 추출된 패턴 (Extracted patterns)
- **Jagged array support** — unlike languages that enforce rectangular grids, Java explicitly allows rows of different lengths within the same 2D array — demonstrated with a 3-element row and a 5-element row coexisting. [S1]
## 📖 세부 내용 (Details)
- Access element: `int[][] myNumbers = { {1, 4, 2}, {3, 6, 8} }; System.out.println(myNumbers[1][2]); // 8`. [S1]
- Row/col sizes: `int[][] myNumbers = { {1, 4, 2}, {3, 6, 8, 5, 2} }; System.out.println(myNumbers.length); // 2 (rows) ... myNumbers[0].length; // 3 ... myNumbers[1].length; // 5`. [S1]
- Nested for: `for (int row = 0; row < myNumbers.length; row++) { for (int col = 0; col < myNumbers[row].length; col++) { System.out.println("myNumbers[" + row + "][" + col + "] = " + myNumbers[row][col]); } }`. [S1]
- Nested for-each: `for (int[] row : myNumbers) { for (int num : row) { System.out.println(num); } }`. [S1]
## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **불규칙 배열(jagged array) 허용**: 행마다 길이가 달라도 유효하다는 점이 예제로 명확히 검증됨. [S1]
## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 표/행렬 형태 데이터 저장 및 순회의 표준 구조다. [S1]
## 💻 코드 패턴 (Code patterns)
Nested for-each over a jagged 2D array (Java):
```java
int[][] myNumbers = { {1, 4, 2}, {3, 6, 8, 5, 2} };
for (int[] row : myNumbers) {
for (int num : row) {
System.out.println(num);
}
}
```
## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.88
- **중복 검사 결과:** 신규 생성 (New discovery)
## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[Java Tutorial]]
- **관련 개념:** [[Java Arrays]], [[Java For Loop Nested]], [[Java Methods]]
- **참조 맥락:** 표/행렬 데이터 구조 — Methods 챕터로 이어짐.
## 📚 출처 (Sources)
- [S1] W3Schools — Java Multi-Dimensional Arrays — https://www.w3schools.com/java/java_arrays_multi.asp
## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "Java Multi-Dimensional Arrays" page (Astra wiki-curation, P-Reinforce v3.1 format).