---
id: java-treemap
title: "Java TreeMap"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["자바 TreeMap"]
duplicate_of: ""
source_trust_level: "B"
confidence_score: 0.89
created_at: 2026-07-04
updated_at: 2026-07-04
review_reason: ""
merge_history: []
tags: ["java", "programming", "w3schools", "collections-framework", "treemap"]
raw_sources: ["https://www.w3schools.com/java/java_treemap.asp"]
applied_in: []
github_commit: ""
---

# [[Java TreeMap]]

## 🎯 한 줄 통찰 (One-line insight)
TreeMap's comparison table reveals a subtle constraint beyond sorting/speed — HashMap allows exactly ONE null key, while TreeMap disallows null keys entirely, since sorting requires comparing keys and `null` has no natural ordering position. [S1]

## 🧠 핵심 개념 (Core concepts)
- **`TreeMap`** — stores key-value pairs sorted automatically by key. [S1]
- **Same API as HashMap** — `put()`, `get()`, `remove()`, `clear()`, `size()`, `keySet()`, `values()`. [S1]
- **No null keys** — unlike HashMap (which allows one null key), TreeMap disallows null keys entirely. [S1]
- **Performance trade-off** — slower than HashMap due to maintaining sort order. [S1]

## 📖 세부 내용 (Details)
- Sorted-by-key output: `TreeMap<String, String> capitalCities = new TreeMap<>(); capitalCities.put("England", "London"); capitalCities.put("Austria", "Wien"); ... // {Austria=Wien, England=London, India=New Dehli, Norway=Oslo, USA=Washington DC} — alphabetically sorted by key`. [S1]
- Comparison table: HashMap (no order, allows one null key, faster) vs. TreeMap (sorted by keys, no null keys, slower). [S1]

## ⚖️ 모순 및 업데이트 (Contradictions & updates)
- **null 키 제약**: HashMap은 null 키를 하나 허용하지만 TreeMap은 전혀 허용하지 않는다는 점이 비교표에서 명확히 구분됨. [S1]

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 알파벳순으로 정렬된 국가-수도 목록이 키 기반 정렬 조회의 대표 사례다. [S1]

## 💻 코드 패턴 (Code patterns)
TreeMap sorts entries alphabetically by key (Java):
```java
TreeMap<String, String> capitalCities = new TreeMap<>();
capitalCities.put("England", "London");
capitalCities.put("Austria", "Wien");
capitalCities.put("India", "New Dehli");
System.out.println(capitalCities);
// {Austria=Wien, England=London, India=New Dehli}
```

## ✅ 검증 상태 및 신뢰도
- **상태:** draft
- **검증 단계:** conceptual
- **출처 신뢰도:** B (W3Schools — widely used educational reference, not a primary standards body)
- **신뢰 점수:** 0.89
- **중복 검사 결과:** 신규 생성 (New discovery)

## 🔗 지식 그래프 (Knowledge Graph)
- **상위/루트:** [[Java Tutorial]]
- **관련 개념:** [[Java HashMap]], [[Java LinkedHashMap]], [[Java TreeSet]]
- **참조 맥락:** 정렬이 필요한 Map 구현체 — LinkedHashMap(삽입 순서 보존) 챕터로 이어짐.

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

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