---
id: java-abstraction
title: "Java Abstraction"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["abstract classes", "자바 추상화"]
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", "abstraction", "abstract-class"]
raw_sources: ["https://www.w3schools.com/java/java_abstract.asp"]
applied_in: []
github_commit: ""
---

# [[Java Abstraction]]

## 🎯 한 줄 통찰 (One-line insight)
An abstract class can freely mix abstract methods (no body) and regular concrete methods (`sleep()` with a real implementation) in the same class — abstraction isn't all-or-nothing; a class can force subclasses to implement SOME behavior while providing shared behavior for the rest. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Abstraction** — hiding implementation details, showing only essential information to the user. [S1]
- **Two mechanisms** — abstract classes or interfaces (interfaces covered next chapter). [S1]
- **Abstract class** — cannot be instantiated directly; must be inherited to be used. [S1]
- **Abstract method** — declared in an abstract class, has no body; the subclass supplies the body. [S1]
- **Mixed abstract class** — can contain BOTH abstract methods and fully-implemented regular methods. [S1]

## 📖 세부 내용 (Details)
- Abstract class definition: `abstract class Animal { public abstract void animalSound(); public void sleep() { System.out.println("Zzz"); } }`. [S1]
- Cannot instantiate: `Animal myObj = new Animal(); // error`. [S1]
- Subclass provides the body: `class Pig extends Animal { public void animalSound() { System.out.println("The pig says: wee wee"); } } ... Pig myPig = new Pig(); myPig.animalSound(); myPig.sleep();`. [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 보안(중요 세부사항만 노출)을 위한 설계 원칙으로 소개된다. [S1]

## 💻 코드 패턴 (Code patterns)
Abstract class mixing abstract and regular methods (Java):
```java
abstract class Animal {
    public abstract void animalSound(); // no body
    public void sleep() {               // regular method
        System.out.println("Zzz");
    }
}
class Pig extends Animal {
    public void animalSound() {
        System.out.println("The pig says: wee wee");
    }
}
```

## ✅ 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 Non Access Modifiers]], [[Java Polymorphism]], [[Java Interface]]
- **참조 맥락:** 인터페이스와 함께 추상화를 달성하는 두 방법 중 하나 — Interface 챕터로 직접 이어짐.

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

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