Groovy Regex groups (groovy regular Expression Group)

Let's look at an example of a Java regular expression.

Import Java.util.regex.matcher;import Java.util.regex.pattern;public class Testmatch {public    static void main ( String[] (args) {        pattern pattern = pattern.compile ("g.*");          Matcher Matcher = Pattern.matcher ("Groovy");          System.out.println (Matcher.matches ());}    }

In fact, this code means that groovy is not a match for regular expressions g.*

For a simple judgment is not a match, write so much code. See how groovy is implemented.

Matcher = "Groovy" =~/g.*/

println (Matcher.matches ())

2 lines of code are done.

How does the regular expression group (regex groups) work? Let's look at a groovy example.

Text = "" "
Lorem ipsum dolor sit amet, consectetuer adipiscing elit.
"""

HOUR =/10|11|12| [0-9]/
MINUTE =/[0-5][0-9]/
AM_PM =/am| pm/
Time =/($HOUR):($MINUTE) ($AM _pm)/

Matcher = text =~ time

println (matcher[0] = = ["1:30pm", "1", "+", "PM"])//first Match

println (matcher[0][0] = = "5:00pm")//first Match Group in the first match
println (matcher[0][1] = = "1")//second Match Group in the first match (HOUR)
println (matcher[0][2] = = "a")//third Match Group in the first match (MINUTE)
println (matcher[0][3] = = "PM")//fourth Match Group in the first match (AM_PM)

println (matcher[1] = = ["12:00pm", "+", "xx", "PM"])//second Match
println (matcher[1][0] = = "12:00pm")//first Match Group in the second match
println (matcher[1][1] = = "a")//second Match Group in the Second match (HOUR)
println (matcher[1][2] = = "xx")//third Match Group in the second match (MINUTE)
println (matcher[1][3] = = "PM")//fourth Match Group in the second match (AM_PM)

Where time can be thought of as a regular expression group, it has three "members": ($HOUR), ($MINUTE), ($AM _pm)

Note that it is a "team member" in (), otherwise each character is a member. Note that a question matcher.matches () means "whether the entire string matches the regular expression", for this example, although there are 2 matches in text, However, the result of Matcher.matches () is false because it does not match the entire string. This detail allows you to understand the role of the regular expression group.

Let's look at an example:

Matcher = ". Groovyd,aa3" =~/(\.groovy.), (AA.) /
println (Matcher.matches ())
println (Matcher.getcount ())

/(\.groovy.), (AA.) /There are 2 "team members"

Let's look at an example:

Matcher = ". Groovyd,aa3" =~/\.groovy.,aa./
println (Matcher.matches ())

/\.GROOVY.,AA./has 12 members.

Resources:

1. http://groovy.codehaus.org/Tutorial+5+-+Capturing+regex+groups

2. Http://groovy.codehaus.org/FAQ+-+RegExp

3. http://developer.51cto.com/art/200906/129179.htm

4. http://docs.oracle.com/javase/7/docs/api/

Groovy Regex groups (groovy regular Expression Group)