Where to store a JWT token?

If you are using REST service and want to store JWT the best way available is SharedPreferences.You should store in PrivateMode for security.
SharedPreference and SharedPreference.Editor is used to store and retrieve JWT. JWT is retrieved after POST request of Username and Password

 private void makeJsonRequest() {    
        String json_req = "json_req";
       // String url = getContext().getString(R.string.LOGIN_URL);
            String url="";    
            final JSONObject obj=new JSONObject();
            try{
                obj.put("username",name);
                obj.put("password",pass);

            }catch (JSONException e)
            {
                e.printStackTrace();
            }

        JsonObjectRequest req = new JsonObjectRequest(Request.Method.POST, url, obj,
                new Response.Listener<JSONObject>() {
                    @Override
                    public void onResponse(JSONObject response) {                          
                    }
                },
                new Response.ErrorListener() {
                    @Override
                    public void onErrorResponse(VolleyError error) {                
                    }

                }) {          
            @Override
            public Map<String, String> getHeaders() throws AuthFailureError {
                Map<String, String> headers = new HashMap<>();
                return headers;
            }
        };
        AppController.getInstance().addToRequestQueue(req, json_req);  

To retrieve JWT from response and save in shared preference use

SharedPreferences prefs;
    SharedPreferences.Editor edit;
 prefs=getActivity().getSharedPreferences("myPrefs",Context.MODE_PRIVATE);
        edit=prefs.edit();
 try {
                         String saveToken=response.getString("token");
                            edit.putString("token",saveToken);
                            Log.i("Login",saveToken);
                              edit.commit();
                        }
                        catch (JSONException e)
                        {
                            e.printStackTrace();
                        }  

To get Token from SharedPreference

private void getToken() {
        prefs=this.getActivity().getSharedPreferences("myPrefs",Context.MODE_PRIVATE);
        String token = prefs.getString("token","");
    }

I found this ans here (src)

If you’re writing an Android app, for instance, you’ll want to store all access tokens in SharedPreferences (here’s the API docs you need to make it work). If you’re an iOS developer, you will want to store your access tokens in the Keychain.

for ios

for android