import java.util.*;
import java.lang.*;
import java.io.*;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
 
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String regex = "\\b[A-Z0-9]{4,8}(?:\\h+(?:[A-Z0-9]{2}|[A-Z]))?\\b";
		String string = "A1B1C1 ABCD E FGHI JK";
 
		Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
		Matcher matcher = pattern.matcher(string);
 
		while (matcher.find()) {
		    System.out.println(matcher.group(0));
		}
	}
}

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