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The regular form of the expressionThe normal form: basic knowledge1 characters, 2 character class, 3 pre-defined character class, 4 Boundary match, 5 greedy number of words, 6 Logical operator
Specific explanations:
1 characters
XCharacter X
\\ Backslash character
\0nCharacters with octal value 0 N (0 <= n <= 7)
\0nnCharacter nn with octal value 0 (0 <= n <= 7)
\0mnnCharacters with octal value 0 mnn (0 <= m <= 3, 0 <= n <= 7)
\xhhCharacter hh with hexadecimal value of 0x
\uhhhhCharacter with hexadecimal value of 0x HHHH
\ ttab (' \u0009 ')
\ nNew lines (line break) (' \u000a ')
\ rCarriage return character (' \u000d ')
\fPage break (' \u000c ')
\aAlarm (Bell) character (' \u0007 ')
\eEscape character (' \u001b ')
\cxThe control corresponding to X
2 Character class
[ABC]a|b | C (Simple Class)
[^ABC]No matter what character.exceptA, B or C (negative)
[A-za-z]A to Z or A to Z, the letters at both ends are included (range)
[A-d[m-p]]A to D or M to P:[a-dm-p] (set)
[A-z&&[def]] D, E or F (intersection)
[A-Z&&[^BC]] A to Z, except B and C:[ad-z] (minus)
[A-z&&[^m-p]]A to Z. Rather than M to P:[a-lq-z] (minus)
3 defining character classes in advance
. Regardless of character (may or may not match the line terminator)
\dNumber: [0-9]
\dNon-numeric: [^0-9]
\swhitespace characters: [\t\n\x0b\f\r]
\sNon-whitespace characters: [^\s]
\w word character: [a-za-z_0-9]
\w non-word characters: [^\w]
4 Boundary Matching Device
^ The beginning of the line
End of the $ line
\bWord boundaries
\bNon-word boundary
\aStart of input
\gEnd of last match
\zThe end of the input, only for the last terminator (if any)
\zEnd of input
5 Greedy Quantity Words
X?
X, not once or once
x* X, 0 or more times
x+X, one or more times
X{n} X, exactly n times
X{n,} X, at least n times
X{N,M} X, at least n times. But no more than M-times
6 Logical operator
XY X followed by Y
X| Y X or Y
(x) x, as capturing group
Like what:the regular form of an email address: //Exact match
String reg = "[a-za-z0-9_]{6,12}@[a-za-z0-9]{3,6} (\\.[ a-za-z]+) {1,3} ";
A general match
String REG1 = "\\w+@\\w+ (\\.\\w+) +";
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Dark Horse Program Ape-------------of Java Network Technology (DAY06)
