---
id: java-packages
title: "Java Packages"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["import keyword", "자바 패키지"]
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", "oop", "packages", "import"]
raw_sources: ["https://www.w3schools.com/java/java_packages.asp"]
applied_in: []
github_commit: ""
---

# [[Java Packages]]

## 🎯 한 줄 통찰 (One-line insight)
Building your own package requires a two-step compile that most beginners miss — first `javac MyPackageClass.java`, then `javac -d . MyPackageClass.java` (the `-d` flag actually creates the package's folder structure); skipping the second step means the package folder never materializes. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Package** — groups related classes, like a folder; avoids name conflicts, improves maintainability. [S1]
- **Built-in packages** — the Java API, a library of prewritten classes (e.g. `java.util`). [S1]
- **User-defined packages** — created via the `package` keyword, mapped to actual filesystem directories. [S1]
- **`import`** — `import package.name.Class;` for a single class, `import package.name.*;` for the whole package. [S1]
- **`-d` compiler flag** — specifies the destination folder, forcing the compiler to create the package directory structure. [S1]
- **Lowercase package naming convention** — avoids conflicts with class names (which start uppercase). [S1]

## 📖 세부 내용 (Details)
- Import a single class: `import java.util.Scanner; ... Scanner myObj = new Scanner(System.in); String userName = myObj.nextLine();`. [S1]
- Import whole package: `import java.util.*;`. [S1]
- User-defined package: `package mypack; class MyPackageClass { public static void main(String[] args) { System.out.println("This is my package!"); } }`. [S1]
- Compile + run: `javac MyPackageClass.java` then `javac -d . MyPackageClass.java`, then run via `java mypack.MyPackageClass`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — Scanner 클래스를 이용한 사용자 입력 처리가 java.util 패키지 활용의 대표 실전 사례다. [S1]

## 💻 코드 패턴 (Code patterns)
Using Scanner from java.util for user input (Java):
```java
import java.util.Scanner;
class Main {
    public static void main(String[] args) {
        Scanner myObj = new Scanner(System.in);
        System.out.println("Enter username");
        String userName = myObj.nextLine();
        System.out.println("Username is: " + userName);
    }
}
```

## ✅ 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 Encapsulation]], [[Java Inheritance]], [[Java User Input]]
- **참조 맥락:** 클래스 그룹화 및 import 문법 — 사용자 입력(Scanner)/상속 챕터로 이어짐.

## 📚 출처 (Sources)
- [S1] W3Schools — Java Packages & API — https://www.w3schools.com/java/java_packages.asp

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