NullPointerException deserializing with gson

问题

I have a JSON that contains the following:

{"p1":{"debris":{"titanium":0,"silicum":0}},"p2":{"debris":{"titanium":0,"silicum":0}}...

I declare the data using HashMap:

public class Galax  {

    public HashMap <String, InnerObject> pos;
}

public class InnerObject {

    public Debris debris;
}

public class Debris {

    public double titanium, silicum;
}

And I call the data using this:

        Galax galax = new Gson().fromJson(strGalaxy, Galax.class);
        System.out.println(galax.pos.get("p2").debris.titanium);

The problem is that I always get NullPointerException when trying to show the data in the log... I do not understand why, because I use do it exactly the same way to get data of other JSON and it works perfectly...

What can be the problem?

Thank you in advance!

回答1:

I see "pos" in the code but not in the JSON string. official answer. :-)

来源：https://stackoverflow.com/questions/9963464/nullpointerexception-deserializing-with-gson