---
id: java-operators-arithmetic
title: "Java Operators Arithmetic"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["increment decrement", "자바 산술 연산자"]
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", "operators", "arithmetic", "increment"]
raw_sources: ["https://www.w3schools.com/java/java_operators_arithmetic.asp"]
applied_in: []
github_commit: ""
---

# [[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 / int`는 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):
```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).