2nd/10_Wiki/Dev/Topic_Java/Java_If_Else.md

id, title, category, status, verification_status, canonical_id, aliases, duplicate_of, source_trust_level, confidence_score, created_at, updated_at, review_reason, merge_history, tags, raw_sources, applied_in, github_commit

id	title	category	status	verification_status	canonical_id	aliases	duplicate_of	source_trust_level	confidence_score	created_at	updated_at	review_reason	merge_history	tags	raw_sources	applied_in	github_commit
java-if-else	Java If Else	Programming_Language	draft	conceptual		if statement 자바 조건문		B	0.9	2026-07-04	2026-07-04			java programming w3schools conditions if	https://www.w3schools.com/java/java_conditions.asp

Java If Else

🎯 한 줄 통찰 (One-line insight)

Omitting curly braces after if is legal Java but dangerous — only the single next line belongs to the condition, so any subsequent line silently runs unconditionally, which is why the source explicitly recommends always using braces even for one-line bodies. [S1]

🧠 핵심 개념 (Core concepts)

• if (condition) { ... } — executes a block only when the condition evaluates to true. [S1]
• Condition must be boolean — either a boolean expression (x > y) or a boolean variable (isLightOn). [S1]
• Case sensitivity — if must be lowercase; If/IF causes a compile error. [S1]
• Boolean variable shorthand — if (isLightOn) is equivalent to if (isLightOn == true) but shorter. [S1]
• Braceless if — a single-statement body can omit { }, but only the immediately following line is conditional. [S1]

🧩 추출된 패턴 (Extracted patterns)

• Braceless-if trap — if (x > y) System.out.println("a"); System.out.println("b"); runs println("b") unconditionally even though it looks indented under the if — the source calls this a "Potential Problem" and recommends ALWAYS using braces to prevent subtle bugs. [S1]

📖 세부 내용 (Details)

• Basic condition: if (20 > 18) { System.out.println("20 is greater than 18"); }. [S1]
• Variable comparison: int x = 20; int y = 18; if (x > y) { System.out.println("x is greater than y"); }. [S1]
• Equality check: if (x == y) { System.out.println("x is equal to y"); }. [S1]
• Boolean variable directly: boolean isLightOn = true; if (isLightOn) { System.out.println("The light is on."); }. [S1]
• Braceless (risky): if (20 > 18) System.out.println("20 is greater than 18");. [S1]
• Safe pattern: always wrap in { }, even multi-statement blocks. [S1]

⚖️ 모순 및 업데이트 (Contradictions & updates)

• 소스가 직접 경고하는 함정: 중괄호 생략 시 첫 줄만 조건에 속하고 이후 줄은 무조건 실행된다는 점. [S1]

🛠️ 적용 사례 (Applied in summary)

현재 발견된 실제 적용 사례가 없습니다 — else/else if/switch로 이어지는 조건문 체계의 출발점이다. [S1]

💻 코드 패턴 (Code patterns)

Safe if with braces (Java):

int x = 20;
int y = 18;
if (x > y) {
    System.out.println("x is greater than y");
    System.out.println("Both lines are part of the if");
}
System.out.println("I am outside if, not part of if!");

✅ 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 Booleans, Java Else, Java Else If, Java Switch
• 참조 맥락: 조건문 체계의 시작점 — else, else if, switch로 이어진다.

📚 출처 (Sources)

• [S1] W3Schools — Java If ... Else — https://www.w3schools.com/java/java_conditions.asp

📝 변경 이력 (Change history)

• 2026-07-04: Initial draft synthesized from the W3Schools "Java Conditions and If Statements" page (Astra wiki-curation, P-Reinforce v3.1 format).