2nd/10_Wiki/Dev/Topic_Java/Java_Operators_Arithmetic.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-operators-arithmetic	Java Operators Arithmetic	Programming_Language	draft	conceptual		increment decrement 자바 산술 연산자		B	0.9	2026-07-04	2026-07-04			java programming w3schools operators arithmetic increment	https://www.w3schools.com/java/java_operators_arithmetic.asp

Java Operators Arithmetic

🎯 한 줄 통찰 (One-line insight)

Dividing two int values ALWAYS truncates to an integer result (10 / 3 gives 3, not 3.33) — getting a decimal result requires both operands to be double, making this a common source of silent precision loss for beginners. [S1]

🧠 핵심 개념 (Core concepts)

• Arithmetic operators — +, -, *, /, % (modulus), ++ (increment), -- (decrement). [S1]
• Integer division truncates — int / int always yields an int, discarding any remainder. [S1]
• Double division preserves decimals — double / double yields the actual fractional result. [S1]
• ++/-- — increase/decrease a variable by exactly 1. [S1]
• Increment then decrement cancels out — ending value equals the starting value. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Integer division truncation is the classic footgun — 10 / 3 silently gives 3 in Java (as in most statically-typed languages), unlike Python 3 where / always returns a float; this difference trips up developers moving between languages. [S1]
• Counter pattern via ++/-- — tracking a running count (e.g. people entering/leaving a room) is the canonical real-world use of increment/decrement. [S1]

📖 세부 내용 (Details)

• All operators demoed: int x = 10; int y = 3; println(x + y); println(x - y); println(x * y); println(x / y); println(x % y);. [S1]
• Integer vs. double division: int a = 10; int b = 3; System.out.println(a / b); // 3 (truncated) vs. double c = 10.0d; double d = 3.0d; System.out.println(c / d); // 3.333.... [S1]
• Increment/decrement counter: int peopleInRoom = 0; peopleInRoom++; peopleInRoom++; peopleInRoom--;. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 정수 나눗셈의 절삭 동작: int / int는 항상 정수 결과를 반환하며 소수점 이하는 버려진다는 점이 명시적으로 경고됨 — Type Casting 챕터의 double 캐스팅 해법과 연결된다. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — 사람 수 카운팅 같은 실전 예제에서 증감 연산자의 용도가 직접 등장한다. [S1]

💻 코드 패턴 (Code patterns)

Integer division truncates, double division doesn't (Java):

int a = 10, b = 3;
System.out.println(a / b);  // 3 (truncated)

double c = 10.0d, d = 3.0d;
System.out.println(c / d);  // 3.333...

✅ 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 Operators, Java Type Casting, Java Numbers
• 참조 맥락: 정수 나눗셈 절삭 문제는 Type Casting 챕터의 double 캐스팅 해법과 직접 연결된다.

📚 출처 (Sources)

• [S1] W3Schools — Java Arithmetic Operators — https://www.w3schools.com/java/java_operators_arithmetic.asp

📝 변경 이력 (Change history)

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