Question

The following code causes null-pointer exception during execution. It just said null pointer exception.

When I put the hotItem class outside of the function, it works without any problem.

Once I put it into the function, it will cause null pointer exception.

I just want to know why this would happen and what is the life cycle of the class inside a function.

private void getHotItem()
{   
    Gson gsonAdapter = new Gson();
    class hotItem
    {
        private String hotItemPK = ""; 
    }
    Type hotItemType = new TypeToken<List<hotItem>>(){}.getType();
    List<hotItem> hotItemList = new ArrayList<hotItem>();

    try
    {
        itemAccess.getHotItemList();
        itemAccess.start();
        itemAccess.join();
        hotItemList = gsonAdapter.fromJson(returnData, hotItemType);

        if(!hotItemList.isEmpty())
        {
            testText.setText(hotItemList.get(0).hotItemPK.toString());
        }
    }
    catch (InterruptedException e)
    {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }
}

Answer 1

Please Check issue here

Resolution:

I’m guessing you have both gson.jar AND gson-stream.jar on your class path; that won’t work.

The problem is that in Gson 2.1 we have a custom version of JsonReader that adds some secret hooks to make MapTypeAdatperFactory faster; these hooks won’t work with gson-stream.jar’s version of JsonReader.