How to modify values of JsonObject / JsonArray directly?

Strangely, the answer is to keep adding back the property. I was half expecting a setter method. :S

System.out.println("Before: " + obj.get("DebugLogId")); // original "02352"

obj.addProperty("DebugLogId", "YYY");

System.out.println("After: " + obj.get("DebugLogId")); // now "YYY"