String[] Encode/Decode (my attempt)

StringUtil.java

import java.util.*;

public class StringUtil {
    public static String encode (String[] ss) {
      StringBuilder sb = new StringBuilder();
      for (String s : ss) {
        if (sb.length() > 0) 
          sb.append(',');
        if (s != null)
          sb.append(s.replaceAll("\\\\", "\\\\\\\\")
                     .replaceAll(",", "\\\\,"));
      }
      return sb.toString();
    }

    public static String[] decode(String s) {
      List<String> l = new ArrayList<String>();
      for(String st : s.split("(?<!\\\\),"))
        l.add(st.replaceAll("\\\\,", ","));
      return l.toArray(new String[l.size()]);
    }

    public static void main(String[] args) {
      // Without nulls
      System.out.println("* Without nulls");

      System.out.println("Encoded: "+ StringUtil.encode(new String[] {"abc", "xyz", "123,456"}));
      System.out.println("Decoded: ");

      for(String p : StringUtil.decode("abc,xyz,123\\,456"))
        System.out.println(": " + p);

      // With nulls
      System.out.println("* With nulls");

      String encoded = StringUtil.encode(new String[] {"abc", null, "123,456", "String with a \\ in it" });
      System.out.println("Encoded: "+ encoded);
      System.out.println("Decoded: ");

      for(String p : StringUtil.decode(encoded))
        System.out.println(": " + p);
    }
}