---
id: java-inner-classes
title: "Java Inner Classes"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["nested classes", "자바 내부 클래스"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.87
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["java", "programming", "w3schools", "oop", "inner-classes"]
raw_sources: ["https://www.w3schools.com/java/java_inner_classes.asp"]
applied_in: []
github_commit: ""
---

# [[Java Inner Classes]]

## 🎯 한 줄 통찰 (One-line insight)
A `static` inner class breaks the usual inner-class advantage — the source explicitly notes that unlike a regular (non-static) inner class, a static inner class does NOT have access to the outer class's members, trading outer-class access for the ability to instantiate without an outer object (`new OuterClass.InnerClass()` instead of `outer.new InnerClass()`). [S1]

## 🧠 핵심 개념 (Core concepts)
- **Inner (nested) class** — a class defined inside another class, grouping related classes for readability/maintainability. [S1]
- **Access syntax** — `OuterClass.InnerClass myInner = myOuter.new InnerClass();` requires an outer instance first. [S1]
- **Private inner class** — restricts access so outside code cannot instantiate it. [S1]
- **Static inner class** — instantiable without an outer object (`new OuterClass.InnerClass()`), but loses access to outer-class members. [S1]
- **Regular inner class can access outer members** — a non-static inner class's methods can read the outer class's attributes directly. [S1]

## 📖 세부 내용 (Details)
- Basic nesting: `class OuterClass { int x = 10; class InnerClass { int y = 5; } } ... OuterClass myOuter = new OuterClass(); OuterClass.InnerClass myInner = myOuter.new InnerClass(); System.out.println(myInner.y + myOuter.x); // 15`. [S1]
- Private inner class: `private class InnerClass { int y = 5; }` — accessing it from outside causes: `error: OuterClass.InnerClass has private access in OuterClass`. [S1]
- Static inner class: `static class InnerClass { int y = 5; } ... OuterClass.InnerClass myInner = new OuterClass.InnerClass(); // no outer instance needed`. [S1]
- Inner class accessing outer members: `class InnerClass { public int myInnerMethod() { return x; } }` — `x` belongs to the outer class, accessible from inside. [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **static 내부 클래스의 트레이드오프**: 외부 객체 없이 인스턴스화 가능하지만, 외부 클래스 멤버에 접근할 수 없다는 점이 명시적으로 강조됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 관련 클래스를 논리적으로 묶어 가독성을 높이는 설계 패턴이다. [S1]

## 💻 코드 패턴 (Code patterns)
Inner class method accessing outer class attribute (Java):
```java
class OuterClass {
    int x = 10;
    class InnerClass {
        public int myInnerMethod() {
            return 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:** 0.87
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[Java Tutorial]]
- **관련 개념:** [[Java Classes]], [[Java Modifiers]], [[Java Abstraction]]
- **참조 맥락:** 클래스 내부에 클래스를 정의하는 구조 — 추상화(Abstraction) 챕터로 이어짐.

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

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