Learn to compile regular expression into java.util.function.Predicate. This can be useful when you want to perform some operation on matched tokens.
Convert Regex to Predicate
I have list of emails with different domain and I want to perform some operation only on email ids with domain name “example.com”.
Now use Pattern.compile().asPredicate() method to get a predicate from compiled regular expression. This predicate can be used with lambda streams to apply it on each token into stream.
import java.util.Arrays;
import java.util.List;
import java.util.function.Predicate;
import java.util.regex.Pattern;
import java.util.stream.Collectors;
public class RegexPredicateExample {
public static void main(String[] args) {
// Compile regex as predicate
Predicate<String> emailFilter = Pattern
.compile("^(.+)@example.com$")
.asPredicate();
// Input list
List<String> emails = Arrays.asList("[email protected]", "[email protected]",
"[email protected]", "[email protected]");
// Apply predicate filter
List<String> desiredEmails = emails
.stream()
.filter(emailFilter)
.collect(Collectors.<String>toList());
// Now perform desired operation
desiredEmails.forEach(System.out::println);
}
}
Output:
[email protected] [email protected]
Using Regex using Pattern.matcher()
If you want to use good old Pattern.matcher(), then use below code template.
public static void main(String[] args)
{
Pattern pattern = Pattern.compile("^(.+)@example.com$");
// Input list
List<String> emails = Arrays.asList("[email protected]", "[email protected]",
"[email protected]", "[email protected]");
for(String email : emails)
{
Matcher matcher = pattern.matcher(email);
if(matcher.matches())
{
System.out.println(email);
}
}
}
Output:
[email protected] [email protected]
Drop me your questions in comments section.
Happy Learning !!
Comments