RequestQueue queue = Volley.newRequestQueue(context);
//for POST requests, only the following line should be changed to 

StringRequest sr = new StringRequest(Request.Method.GET, "http://headers.jsontest.com/",
  new Response.Listener<String>() {
    @Override
    public void onResponse(String response) {
      Log.e("HttpClient", "success! response: " + response.toString());
    }
  },
  new Response.ErrorListener() {
    @Override
    public void onErrorResponse(VolleyError error) {
      Log.e("HttpClient", "error: " + error.toString());
    }
  })
  {
    @Override
    protected Map<String,String> getParams(){
      Map<String,String> params = new HashMap<String, String>();
      params.put("user","YOUR USERNAME");
      params.put("pass","YOUR PASSWORD");
      return params;
    }
    @Override
    public Map<String, String> getHeaders() throws AuthFailureError {
      Map<String,String> params = new HashMap<String, String>();
      params.put("Content-Type","application/x-www-form-urlencoded");
      return params;
    }
  };
queue.add(sr);