How to search for a pattern in a Java string?

Java provides the java.util.regex package for pattern matching with regular expressions. You can then search for a pattern in a Java string using classes and methods of this packages.

Example

import java.util.regex.Matcher;
import java.util.regex.Pattern;
public class RegexMatches {
   public static void main( String args[] ) {

      String line = "This order was placed for QT3000! OK?";
      String pattern = "(.*)(\d+)(.*)";
      Pattern r = Pattern.compile(pattern);
      Matcher m = r.matcher(line);
     
      if (m.find( )) {
         System.out.println("Found value: " + m.group(0));
         System.out.println("Found value: " + m.group(1));
         System.out.println("Found value: " + m.group(2));
      }else{
         System.out.println("NO MATCH");
      }
   }
}

Output

Found value: This order was placed for QT3000! OK?
Found value: This order was placed for QT300
Found value: 0