Need to use regular expressions (regex) for common tasks in Java?
Here is a quick example:

import java.util.regex.Pattern
import java.util.regex.Matcher
 
// ...
 
Pattern pattern = Pattern.compile("pattern");
Matcher matcher = pattern.matcher("subject");
 
// find (sub)matches
while(matcher.find()) {
    String nth_match = matcher.group();
}
 
// veryfy that the whole subject matches the pattern
Boolean does_it_matches = matcher.matches()
 
// replace all the occurrence of a regex in a String (no import needed)
"string instance".replaceAll("regex","replacement");

For other tasks take a look at the Matcher class javadoc.