---
id: java-files-write
title: "Java Files Write"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["FileWriter", "자바 파일 쓰기"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.88
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["java", "programming", "w3schools", "files", "io", "write", "filewriter"]
raw_sources: ["https://www.w3schools.com/java/java_files_write.asp"]
applied_in: []
github_commit: ""
---

# [[Java Files Write]]

## 🎯 한 줄 통찰 (One-line insight)
FileWriter OVERWRITES a file by default — appending requires explicitly passing `true` as a SECOND constructor argument (`new FileWriter("filename.txt", true)`), which is easy to miss since the single-argument constructor silently discards existing content. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`FileWriter`** — the simplest class for writing text to a file. [S1]
- **`.write(text)` + `.close()`** — writes then must manually close (or use try-with-resources). [S1]
- **Default behavior: overwrite** — an existing file's content is replaced unless append mode is used. [S1]
- **Append mode** — pass `true` as the second constructor argument: `new FileWriter("filename.txt", true)`. [S1]
- **Auto-creation** — if the file doesn't exist, Java creates it before appending. [S1]
- **Alternative write classes** — FileWriter (easiest, basic text), BufferedWriter (faster, better for large files), FileOutputStream (best for binary data). [S1]

## 📖 세부 내용 (Details)
- Basic write with manual close: `FileWriter myWriter = new FileWriter("filename.txt"); myWriter.write("Files in Java might be tricky, but it is fun enough!"); myWriter.close();`. [S1]
- Try-with-resources (auto-close): `try (FileWriter myWriter = new FileWriter("filename.txt")) { myWriter.write("..."); } catch (IOException e) {...}`. [S1]
- Append mode: `try (FileWriter myWriter = new FileWriter("filename.txt", true)) { myWriter.write("\nAppended text!"); }`. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **기본 동작이 덮어쓰기**: 추가(append)하려면 반드시 두 번째 인자로 true를 전달해야 한다는 점이 강조됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 로그 파일에 내용을 추가하는 등 append 모드는 실전에서 자주 쓰이는 패턴이다. [S1]

## 💻 코드 패턴 (Code patterns)
Append mode via the two-argument FileWriter constructor (Java):
```java
try (FileWriter myWriter = new FileWriter("filename.txt", true)) { // true = append
    myWriter.write("\nAppended text!");
    System.out.println("Successfully appended to the file.");
} catch (IOException e) {
    System.out.println("An error occurred.");
}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.88
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[Java Tutorial]]
- **관련 개념:** [[Java Files Create]], [[Java Files Read]], [[Java BufferedWriter]], [[Java FileOutputStream]]
- **참조 맥락:** 파일에 텍스트 쓰기 — Read 챕터로 이어지며, BufferedWriter/FileOutputStream은 후속 챕터에서 심화.

## 📚 출처 (Sources)
- [S1] W3Schools — Java Write To Files — https://www.w3schools.com/java/java_files_write.asp

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