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2026-07-05 00:39:13 +09:00

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title

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):

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).

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