---
id: java-regex
title: "Java RegEx"
category: "Programming_Language"
status: "draft"
verification_status: "conceptual"
canonical_id: ""
aliases: ["regular expressions", "자바 정규표현식"]
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", "regex"]
raw_sources: ["https://www.w3schools.com/java/java_regex.asp"]
applied_in: []
github_commit: ""
---

# [[Java RegEx]]

## 🎯 한 줄 통찰 (One-line insight)
Java has no built-in Regular Expression type — like dates, regex requires importing `java.util.regex` (Pattern + Matcher classes), and the search flow is explicitly two-step: `Pattern.compile()` builds the pattern object first, then `.matcher(text).find()` runs the actual search against a specific string, decoupling "what to search for" from "where to search." [S1]

## 🧠 핵심 개념 (Core concepts)
- **Regular expression** — a sequence of characters forming a search pattern for text search/replace. [S1]
- **`java.util.regex` package** — required import; contains `Pattern`, `Matcher`, `PatternSyntaxException`. [S1]
- **`Pattern.compile(regex, flags)`** — builds the pattern; flags are optional (e.g. `Pattern.CASE_INSENSITIVE`). [S1]
- **`pattern.matcher(text)`** — returns a `Matcher` bound to a specific string. [S1]
- **`matcher.find()`** — returns true/false depending on whether the pattern matches. [S1]
- **Bracket expressions** — `[abc]` (any of a/b/c), `[^abc]` (none of a/b/c), `[0-9]` (digit range). [S1]
- **Metacharacters** — `|` (alternation), `.` (any char), `^`/`$` (start/end anchors), `\d` (digit), `\s` (whitespace), `\b` (word boundary), `\uxxxx` (Unicode). [S1]
- **Quantifiers** — `n+`, `n*`, `n?`, `n{x}`, `n{x,y}`, `n{x,}`. [S1]

## 📖 세부 내용 (Details)
- Basic case-insensitive search: `Pattern pattern = Pattern.compile("w3schools", Pattern.CASE_INSENSITIVE); Matcher matcher = pattern.matcher("Visit W3Schools!"); boolean matchFound = matcher.find(); // true`. [S1]
- Flags: `Pattern.CASE_INSENSITIVE`, `Pattern.LITERAL` (treats special chars as ordinary), `Pattern.UNICODE_CASE` (extends case-insensitivity beyond English). [S1]

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

## 🛠️ 적용 사례 (Applied in summary)
현재 발견된 실제 적용 사례가 없습니다 — 대소문자 구분 없이 특정 단어의 존재 여부를 검사하는 것이 정규표현식의 가장 기본적인 실전 활용이다. [S1]

## 💻 코드 패턴 (Code patterns)
Case-insensitive pattern search (Java):
```java
import java.util.regex.Matcher;
import java.util.regex.Pattern;

Pattern pattern = Pattern.compile("w3schools", Pattern.CASE_INSENSITIVE);
Matcher matcher = pattern.matcher("Visit W3Schools!");
boolean matchFound = matcher.find(); // true
```

## ✅ 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 Annotations]], [[Java Strings]], [[Java Threads]]
- **참조 맥락:** 텍스트 검색/치환의 표준 도구 — 스레드(Threads) 챕터로 이어짐.

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

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