Convert a JSON string to object in Java ME?

The simplest option is Jackson:

MyObject ob = new ObjectMapper().readValue(jsonString, MyObject.class);

There are other similarly simple to use libraries (Gson was already mentioned); but some choices are more laborious, like original org.json library, which requires you to create intermediate "JSONObject" even if you have no need for those.

I used a few of them and my favorite is,

http://code.google.com/p/json-simple/

The library is very small so it's perfect for J2ME.

You can parse JSON into Java object in one line like this,

JSONObject json = (JSONObject)new JSONParser().parse("{\"name\":\"MyNode\", \"width\":200, \"height\":100}");
System.out.println("name=" + json.get("name"));
System.out.println("width=" + json.get("width"));