일부 내용은 손에 잡히는 정규 표현식에서 발췌

수량자.

과하게 일치하는 상황 방지

• Greedy Qualifier : 최대로 일치
• Lazy Qualifier : 최소로 일치

(?i)<b>.*</b>

(?i)<b>.*?</b>

괄호로 감싼 하위 표현식을 참조하는 정규 표현식. $1~n 으로 표현. (일부 언어는 $대신 /을 사용하기도 한다.)

변수와 비슷.

String eg1 = "Hello, xxx@xxx.com is my email address.";
String result1 = eg1.replaceAll("(\\w+[\\w.]*@[\\w.]+\\.\\w+)", "<a href=\"$1\">$1</href>");
System.out.println(result1); // Hello, <a href="ben@forta.com">ben@forta.com</href> is my email address.

String eg2 = "031-123-1234";
String result2 = eg2.replaceAll("(\\d{3})(-)(\\d{3})(-)(\\d{4})", "($1) $3-$5");
System.out.println(result2); // (031) 123-1234

https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html

Pattern p = Pattern.compile("^REGULAR_EXPRESSION$", Pattern.CASE_INSENSITIVE); // regex, pattern
Matcher m = p.matcher(STRING);
boolean b = m.matches();

Pattern.CASE_INSENSITIVE    (?i)
Pattern.COMMENTS            (?x)
Pattern.MULTILINE           (?m)
Pattern.DOTALL              (?s)
Pattern.LITERAL             None
Pattern.UNICODE_CASE        (?u)
Pattern.UNIX_LINES          (?d)

\p{Lower}	A lower-case alphabetic character: [a-z]
\p{Upper}	An upper-case alphabetic character:[A-Z]
\p{ASCII}	All ASCII:[\x00-\x7F]
\p{Alpha}	An alphabetic character:[\p{Lower}\p{Upper}]
\p{Digit}	A decimal digit: [0-9]
\p{Alnum}	An alphanumeric character:[\p{Alpha}\p{Digit}]
\p{Punct}	Punctuation: One of !"#$%&'()*+,-./:;<=>?@[\]^_`{|}~
\p{Graph}	A visible character: [\p{Alnum}\p{Punct}]
\p{Print}	A printable character: [\p{Graph}\x20]
\p{Blank}	A space or a tab: [ \t]
\p{Cntrl}	A control character: [\x00-\x1F\x7F]
\p{XDigit}	A hexadecimal digit: [0-9a-fA-F]
\p{Space}	A whitespace character: [ \t\n\x0B\f\r]

^(02|0[3-6]{1}[1-5]{1})-?[0-9]{3,4}-?[0-9]{4}$ //지역번호-xxx(x)-xxxx
^(15(44|77|88|99)|1644)-?[0-9]{4}$ //15xx/1644-xxxx

String str = "(int a, int b)";

Pattern p = Pattern.compile("\\((.*?)\\)");
Matcher m = p.matcher(str);

while(m.find())
	System.out.println(m.group(1));