---
id: java-classes
title: "Java Classes"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["classes and objects", "자바 클래스"]
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", "oop", "classes"]
raw_sources: ["https://www.w3schools.com/java/java_classes.asp"]
applied_in: []
github_commit: ""
---

# [[Java Classes]]

## 🎯 한 줄 통찰 (One-line insight)
Java enforces a strict class-filename match (`Main` must live in `Main.java`), which becomes essential once splitting code across multiple classes/files — the multi-class example explicitly shows `Main.java` holding the data class while `Second.java` holds the class with `main()`. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Class** — an object constructor/"blueprint" for creating objects. [S1]
- **`class` keyword** — declares a class; name should start uppercase and match the filename. [S1]
- **`new` keyword** — creates an object instance from a class: `Main myObj = new Main();`. [S1]
- **Multiple objects** — each independent instance of the same class. [S1]
- **Multiple classes/files** — one class can hold attributes/methods, another can hold `main()` — common organizational pattern. [S1]

## 📖 세부 내용 (Details)
- Class definition: `public class Main { int x = 5; }`. [S1]
- Object creation and access: `Main myObj = new Main(); System.out.println(myObj.x); // 5`. [S1]
- Multiple objects: `Main myObj1 = new Main(); Main myObj2 = new Main();` — each independently prints `x = 5`. [S1]
- Multi-file pattern: `Main.java` defines `class Main { int x = 5; }`; `Second.java` defines `class Second { public static void main(...) { Main myObj = new Main(); System.out.println(myObj.x); } }`; compiled/run via `javac Main.java`, `javac Second.java`, `java Second`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 클래스와 main() 실행 로직을 별도 파일로 분리하는 구조가 이후 OOP 전반의 표준 패턴이다. [S1]

## 💻 코드 패턴 (Code patterns)
Multiple independent objects (Java):
```java
public class Main {
    int x = 5;
    public static void main(String[] args) {
        Main myObj1 = new Main(); // Object 1
        Main myObj2 = new Main(); // Object 2
        System.out.println(myObj1.x);
        System.out.println(myObj2.x);
    }
}
```

## ✅ 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 OOP]], [[Java Class Attributes]], [[Java Class Methods]], [[Java Constructors]]
- **참조 맥락:** 클래스 선언/객체 생성의 기초 문법 — 속성/메서드 챕터로 확장.

## 📚 출처 (Sources)
- [S1] W3Schools — Java Classes and Objects — https://www.w3schools.com/java/java_classes.asp

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