Double brace initialization not working

[GoogleCodeExporter]

Map<String, List<String>> jsonData = new HashMap<String, List<String>>();
jsonData.put("test", new ArrayList<String>() {
    {
        add("1");
        add("2");
        add("3");
    }
});
System.out.println(new Gson().toJson(jsonData));
//OUTPUT = {}

Map<String, List<String>> jsonData = new HashMap<String, List<String>>();
ArrayList<String> list = new ArrayList<String>();
list.add("1");
list.add("2");
list.add("3");
jsonData.put("test", list);
System.out.println(new Gson().toJson(jsonData));

//OUTPUT = {"test":["1","2","3"]}

Original issue reported on code.google.com by neyas...@gmail.com on 13 Jul 2011 at 9:39

• Merged into: #298

[GoogleCodeExporter]

The fundamental problem is that you aren't supplying GSON with enough type 
information and so it has to infer the type from the value. You can work-around 
this by providing the type in your call to toJson():

  String json = gson.toJson(jsonData, new TypeToken<Map<String, List<String>>>() {}.getType()));

We still have a problem where GSON never serializes anonymous classes, which is 
an unfortunate policy in this instance.

Original comment by limpbizkit on 1 Oct 2011 at 4:40

• Added labels: Priority-Low
• Removed labels: Priority-Medium

[GoogleCodeExporter]

Original comment by limpbizkit on 2 Oct 2011 at 3:38

• Changed state: Duplicate

[GoogleCodeExporter]

Issue 370 has been merged into this issue.

Original comment by limpbizkit on 19 Oct 2011 at 4:30