/* package whatever; // don't place package name! */
 
import java.util.*;
import java.util.regex.*;
import java.lang.*;
import java.io.*;
 
/* Name of the class has to be "Main" only if the class is public. */
class Ideone
{
	public static void main (String[] args) throws java.lang.Exception
	{
		String src		 = "content (content1 (content2, content3) content4 (content5 (content6, content7))";
		Matcher m		 = Pattern.compile("\\w+(?:,\\s*\\w+)*").matcher(src);
		List<String> res = new ArrayList<>();
		while (m.find()) System.out.println(m.group());
	}
}

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