---
id: java-syntax
title: "Java Syntax"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["main method", "자바 문법"]
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", "syntax", "main-method"]
raw_sources: ["https://www.w3schools.com/java/java_syntax.asp"]
applied_in: []
github_commit: ""
---

# [[Java Syntax]]

## 🎯 한 줄 통찰 (One-line insight)
The filename MUST exactly match the public class name (`Main` → `Main.java`), because Java uses the class name to locate and run the code — a mismatch is a hard error, not a warning. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Every line of runnable code lives inside a class** — class names conventionally start with an uppercase letter. [S1]
- **Case-sensitive** — `MyClass` and `myclass` are different names. [S1]
- **Filename must match the class name** — `class Main` must be saved as `Main.java`. [S1]
- **`main()` method** — required in every Java program; the entry point where execution starts. [S1]
- **`System.out.println()`** — prints a line of text; `System` is a built-in class, `out` is its output member, `println()` is the print-line method. [S1]
- **Semicolons required** — every statement must end with `;`. [S1]
- **Curly braces `{}`** — mark the start/end of a code block. [S1]

## 🧩 추출된 패턴 (Extracted patterns)
- **Filename-class binding is unusually strict** — unlike many languages where filenames are just organizational, Java enforces filename == public class name as a hard requirement for compilation to succeed. [S1]

## 📖 세부 내용 (Details)
- Basic structure: `public class Main { public static void main(String[] args) { System.out.println("Hello World"); } }`, saved as `Main.java`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — public/static/void 키워드는 이후 OOP 챕터(Modifiers)에서 상세히 다뤄진다. [S1]

## 💻 코드 패턴 (Code patterns)
Minimal Java program structure (Java, file: Main.java):
```java
public class Main {
    public static void main(String[] args) {
        System.out.println("Hello World");
    }
}
```

## ✅ 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 Intro]], [[Java Statements]], [[Java Modifiers]]
- **참조 맥락:** Java 프로그램의 기본 골격 — public/static/void는 이후 Modifiers 챕터로 이어진다.

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

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