Java Regular Expressions

1, [ABC] A, B or C

[^ABC] Any character except A, B or C

[A-za-z] A to Z or A to Z, both characters are included

[A-d[m-p]] A to D or M to P: [A-dm-p] (set)

[A-z&&[def]] d,e or F (intersection)

2, * any character

\d number: [0-9]

\d non-numeric: [^0-9]

\s whitespace characters: [\t\n\x0b\f\r]

\s non-whitespace characters: [^\s]

\w Word character: [a-za-z_0-9]

\w non-word characters: [^\w]

3, greedy number of words

X? Not once or once.

x* 0 or more times

x+ one or more times

X{n} exactly n times

X{n,} at least n times

X{n,m} at least n times, but not more than M string

4, replace function

String s = "Hello123world";

String regex = "\\d";

String s2 = s.replaceall (Regex, "");

5, grouping function

Capturing groups can be numbered by calculating their opening brackets from left to right, ((A) (B (C))) There are 4 such groups

1 ((A) (B (C)))

2 (A)

3 (B (C))

4 (C)

Application: Overlapping word cutting: "SDQQFGKKKHJPPPPKL";

String regex = "(.) \\1+ "; string[] arr = s.split (regex);

Application: Put the string "I I ...." I... I-I-I ... Want to ... To learn .... Learn to learn. School of learning, knitting, knitting, knitting, ... Regulation Regulation ... "Output as" I want to learn to program "

String s = "I am ...." I... I-I-I ... Want to ... To learn .... Learn to learn. School of learning, knitting, knitting, knitting, ... Regulation Regulation ... Process ";

String s2 = s.replaceall ("\\.+", "" ");

String s3 = S2.replaceall ("(.) \\1+ "," $ ");

6, pattern and Matcher

Pattern p = pattern.compile (a*b); Get to Regular expression

Matcher m = P.matcher ("Aaaaaab"); Get the matching device

Boolean B = m.matches (); To see if it matches, the match returns True.

　　 Equivalent to System.out.println ("Aaaaaab". Matches ("A*b"));

Apply: Get the phone number in a string

String s = "My phone number is 18988888888, has used 18987654321, also used 18812345678";

String regex = "1[3578]\\d{9}";

Pattern p = pattern.compile (regex);

Matcher m = P.matcher (s);

while (M.find ()) System.out.println (M.group ()); We have to find the group first.

Java Regular Expressions