Unable to put null values in JSON object

Right there in the documentation, in the first paragraph:

Values may not be null, NaNs, infinities, or of any type not listed here.

So yes, it is “…something that null values are not included…” (edit: that was a quote from your original question; your updated question changes it to “uninitialized values” but the default value of an object reference is null, so…)

It’s a “feature” of that class, though; JSON itself understands null just fine. Further down in the documentation it says you use a “sentinal value,” NULL, to represent null. Which seems…odd. There’s a note about it:

Warning: this class represents null in two incompatible ways: the standard Java null reference, and the sentinel value NULL. In particular, calling put(name, null) removes the named entry from the object but put(name, JSONObject.NULL) stores an entry whose value is JSONObject.NULL.

So:

params.put(KEY_TOKEN, token == null ? JSONObject.NULL : token);