---
id: java-variables
title: "Java Variables"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["자바 변수"]
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", "variables"]
raw_sources: ["https://www.w3schools.com/java/java_variables.asp"]
applied_in: []
github_commit: ""
---

# [[Java Variables]]

## 🎯 한 줄 통찰 (One-line insight)
Unlike Python, Java is statically typed — every variable declaration must state a type (`type variableName = value;`), and that type cannot silently change later the way Python's dynamic typing allows. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Basic types** — `String` (text, double-quoted), `int` (whole numbers), `float` (decimals), `char` (single character, single-quoted), `boolean` (true/false). [S1]
- **Declaration syntax** — `type variableName = value;`. [S1]
- **Declare-then-assign** — `int myNum; myNum = 15;` is also valid, splitting declaration and assignment. [S1]
- **Reassignment overwrites** — assigning a new value replaces the old one. [S1]
- **`final` keyword** — makes a variable unchangeable/read-only; reassigning raises a compile error. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Static typing is the core Java/Python divergence** — every Java variable's type is fixed at declaration and enforced by the compiler, unlike Python where `x = 4; x = "Sally"` is legal. [S1]

## 📖 세부 내용 (Details)
- String declaration: `String name = "John"; System.out.println(name);`. [S1]
- Int declaration: `int myNum = 15;`. [S1]
- Separate declare/assign: `int myNum; myNum = 15;`. [S1]
- Reassignment: `int myNum = 15; myNum = 20;`. [S1]
- final (immutable): `final int myNum = 15; myNum = 20; // error`. [S1]
- All basic types together: `int myNum = 5; float myFloatNum = 5.99f; char myLetter = 'D'; boolean myBool = true; String myText = "Hello";`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
소스에서 모순되는 정보는 발견되지 않음.

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 이후 Data Types 챕터에서 각 타입이 상세히 다뤄진다. [S1]

## 💻 코드 패턴 (Code patterns)
Five basic types declared (Java):
```java
int myNum = 5;
float myFloatNum = 5.99f;
char myLetter = 'D';
boolean myBool = true;
String myText = "Hello";
```

## ✅ 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 Data Types]], [[Java Constants Final]], [[Python Variables]]
- **참조 맥락:** 정적 타이핑이라는 Java의 핵심 특성 — Python의 동적 타이핑과 대비.

## 📚 출처 (Sources)
- [S1] W3Schools — Java Variables — https://www.w3schools.com/java/java_variables.asp

## 📝 변경 이력 (Change history)
- 2026-07-04: Initial draft synthesized from the W3Schools "Java Variables" page (Astra wiki-curation, P-Reinforce v3.1 format).