View Category
Regex
Matching

Check if a string matches a regular expression

Display "ok" if "Hello" matches /[A-Z][a-z]+/
perl
print 'ok' if ('Hello' =~ /[A-Z][a-z]+/);
java
if ("Hello".matches("[A-Z][a-z]+")) {
System.out.println("ok");
}
groovy
if ("Hello" =~ /[A-Z][a-z]+/) println 'ok'
if ("Hello".find(/[A-Z][a-z]+/)) println 'ok'
// with precompiled regex
def regex = ~/[A-Z][a-z]+/
if ("Hello".find(regex)) println 'ok'
// with precompiled regex
def regex = ~/[A-Z][a-z]+/
if ("Hello".matches(regex)) println 'ok'
if ("Hello".matches("[A-Z][a-z]+")) println 'ok'

Check if a string matches with groups

Display "two" if "one two three" matches /one (.*) three/
perl
print $1 if "one two three"=~/^one (.*) three$/
java
Pattern pattern = Pattern.compile("one (.*) three");
Matcher matcher = pattern.matcher("one two three");
if (matcher.matches()) {
System.out.println(matcher.group(1));
}
groovy
matcher = ("one two three" =~ /one (.*) three/)
if (matcher) println matcher[0][1]
match = "one two three".find("one (.*) three") { it[1] }
if (match) println match
Searching

Check if a string contains a match to a regular expression

Display "ok" if "abc 123 @#$" matches /\d+/
perl
print "ok" if ("abc 123 @#\$" =~ m/\d+/)
java
Pattern pattern = Pattern.compile("\\d+");
Matcher matcher = pattern.matcher(text);
if (matcher.find()) {
System.out.println("ok");
}
groovy
if ('abc 123 @#$' =~ /\d+/) println 'ok'
if ('abc 123 @#$'.find(/\d+/)) println 'ok'

Loop through a string matching a regex and performing an action for each match

Create a list [fish1,cow3,boat4] when matching "(fish):1 sausage (cow):3 tree (boat):4" with regex /\((\w+)\):(\d+)/
perl
while ($text =~ /\((\w+)\):(\d+)/g) {
push @list, "$1$2"
}
java
List list = new ArrayList();
Pattern pattern = Pattern.compile("\\((\\w+)\\):(\\d+)");
Matcher matcher = pattern.matcher(text);
while(matcher.find()) {
list.add(matcher.group(1)+matcher.group(2));
}
groovy
list = (text =~ /\((\w+)\):(\d+)/).collect{ it[1] + it[2] }
list = []
text.eachMatch(/\((\w+)\):(\d+)/){
list << it[1] + it[2]
}
list = []
text.eachMatch(/\((\w+)\):(\d+)/){ m, name, number ->
list << "$name$number"
}
list = (text =~ /\((\w+)\):(\d+)/).collect{ all, name, num -> "$name$num" }
list = text.findAll(regex){ _, name, num -> "$name$num" }
list = text.findAll(regex){ it[1] + it[2] }
Replacing

Replace the first regex match in a string with a static string

Transform "Red Green Blue" into "R*d Green Blue" by replacing /e/ with "*"
perl
$text =~s/e/*/;
java
String replaced = "Red Green Blue".replaceFirst("e", "*");
groovy
replaced = "Red Green Blue".replaceFirst("e", "*")

Replace all regex matches in a string with a static string

Transform "She sells sea shells" into "She X X shells" by replacing /se\w+/ with "X"
perl
$text = "She sells sea shells";
$text =~ s/se\w+/X/g;
java
String replaced = text.replaceAll("se\\w+", "X");
groovy
replaced = text.replaceAll(/se\w+/,"X")

Replace all regex matches in a string with a dynamic string

Transform "The {Quick} Brown {Fox}" into "The kciuQ Brown xoF" by reversing words in braces using the regex /\{(\w+)\}/.
perl
$text = "The {Quick} Brown {Fox}";
$text =~ s/\{(\w+)\}/reverse($1)/ge;
java
Matcher m = Pattern.compile("\\{(\\w+)\\}").matcher("The {Quick} Brown {Fox}");
StringBuffer sb = new StringBuffer(32), rsb = new StringBuffer(8);

while (m.find())
{
rsb.replace(0, rsb.length(), m.group(1)); rsb.reverse(); m.appendReplacement(sb, rsb.toString());
}
m.appendTail(sb);
groovy
replaced = "The {Quick} Brown {Fox}".replaceAll(/\{(\w+)\}/, { full, word -> word.reverse() } )