---
id: java-data-structures
title: "Java Data Structures"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["자바 자료구조 개요"]
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", "data-structures"]
raw_sources: ["https://www.w3schools.com/java/java_data_structures.asp"]
applied_in: []
github_commit: ""
---

# [[Java Data Structures]]

## 🎯 한 줄 통찰 (One-line insight)
The choice between ArrayList/HashSet/HashMap comes down to a single 3-column decision table (order-kept? duplicates-allowed? best-for) — order+duplicates → ArrayList, uniqueness → HashSet, key-based lookup → HashMap, giving a fast heuristic before diving into each structure's details. [S1]

## 🧠 핵심 개념 (Core concepts)
- **Data structure** — a way to store/organize data efficiently; arrays are the simplest example. [S1]
- **`ArrayList`** — resizable array; keeps insertion order; allows duplicates; access by index. [S1]
- **`HashSet`** — every element unique; adding a duplicate is silently ignored; no fixed order. [S1]
- **`HashMap`** — stores key-value pairs for fast lookup by key; keys unique, values can duplicate. [S1]
- **Iterator** — a standard way to loop through any data structure via `hasNext()`/`next()`. [S1]

## 📖 세부 내용 (Details)
- ArrayList: `ArrayList<String> cars = new ArrayList<String>(); cars.add("Volvo"); cars.add("BMW"); ...`. [S1]
- HashSet dedup: `HashSet<String> cars = new HashSet<String>(); cars.add("BMW"); cars.add("BMW"); // duplicate ignored`. [S1]
- HashMap key-value: `HashMap<String, String> capitalCities = new HashMap<String, String>(); capitalCities.put("England", "London"); ...`. [S1]
- Iterator loop: `Iterator<String> it = cars.iterator(); while(it.hasNext()) { System.out.println(it.next()); }`. [S1]
- Comparison table: ArrayList (ordered, duplicates OK, index access), HashSet (unique, no order, fast checks), HashMap (key-value, no order, fast key lookup). [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 국가-수도 매핑(HashMap)이 키 기반 조회의 대표 예시다. [S1]

## 💻 코드 패턴 (Code patterns)
Quick comparison: ArrayList, HashSet, HashMap (Java):
```java
ArrayList<String> cars = new ArrayList<String>(); // ordered, duplicates OK
HashSet<String> uniqueCars = new HashSet<String>(); // unique only
HashMap<String, String> capitalCities = new HashMap<String, String>(); // key-value
```

## ✅ 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 Collections]], [[Java List]], [[Java Set]], [[Java Map]], [[Java Iterator]]
- **참조 맥락:** 자료구조 전체 섹션의 개념적 도입부 — Collections Framework 챕터로 이어짐.

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

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