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 = "(?:^(\\w+)=|\\G(?!^))(\\w+)(?:,|$)";
        Pattern pattern = Pattern.compile(regex, Pattern.MULTILINE);
        String[] strings = {"Something=Item1,Item2,Item3", "someOtherThing=Some_Item", "Something="};
 
        for (String s : strings) {
            Matcher matcher = pattern.matcher(s);
 
            while (matcher.find()) {
                String gr1 = matcher.group(1);
                String gr2 = matcher.group(2);
 
                if (gr1 != null) {
                    System.out.println("Group 1: " + gr1);
                }
                if (gr2 != null) {
                    System.out.println("Group 2: " + gr2);
                }
            }
        }
	}
}

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