JSONArray parameter=main.getJSONArray("parameter");
float[] avgTemp=new float[24];

//for 24 hours of the day
for(int i=0;i<24;i++){
     int occurence=0;
     float totalTemp=0;
     for(int j=0;j<parameter.size();j++){
          int time=convertTime(parameter.get(j).getString("time"));
          if(time==i){
               totalTemp+=Float.parseFloat(parameter.get(j).getString("temp"));
               occurence++;
              }
         avgTemp[i]=(totalTemp/occurence);
         }
    }

最后，你将得到数组中所有特定时间的平均温度

Something like this could be useful for you

Map<int, double[]> timeAndTemp = new HashMap<int,double[]>();    
String jSONData = *your json read as string*;
try (InputStream is = url.openStream();
JsonReader rdr = Json.createReader(new StringReader(jSONData)) {

    JsonObject obj = rdr.readObject();
    JsonArray results = obj.getJsonArray("parameters");
    for (JsonObject result : results.getValuesAs(JsonObject.class)) {
         int time = convertTime(result.getString("time"));
         double temp = double.parse(result.getString("temp"));
         if(!timeAndTemp.containsKey(time)){
             timeAndTemp.put(time, temp);
         } else {
             timeAndTemp.get(time).add(temp); 
         }
         timeAndTemp.put(time, temp);
    }
}

//then when you fill in all your data in the map you can easily iterate trough it and get all temperatures for a current time and sum them then divide on their number (the formula for an average number)
//here are some simple examples for using JsonReader and JsonWriter http://www.programmingforliving.com/2013/07/java-api-for-json-processing-jee7-p1.html

@vishwaijt palankar，这是我的代码，请检查，当我运行logcat时，有更多的totaltemp和occurrence值。

public class Customadapter extends BaseAdapter {
        Context context;
        ArrayList<Parameter> parameterList;
        ArrayList<Parameter> tempArrayList = new ArrayList<Parameter>();
        long dateLong;
        String numhour;
        int count = 0;
        float sum = 0;
        HashMap<String, Float> tempMap;

        public Customadapter(Context context, int resource,
                ArrayList<Parameter> listParameters, long date) {
            super();
            this.context = context;
            this.dateLong = date;
            this.parameterList = getMyList(listParameters);
            Log.d("size", String.valueOf(parameterList.size()));
        }

        @SuppressWarnings("static-access")
        private ArrayList<Parameter> getMyList(ArrayList<Parameter> list) {
            for (Parameter parameter : list) {
                if (((new ConvertData()).convertDate((parameter.getDate()))) == dateLong) {

                    tempArrayList.add(parameter);
                }
            }

            return tempArrayList;
        }

        @Override
        public int getCount() {
            // TODO Auto-generated method stub
            return parameterList.size();
        }

        @Override
        public Object getItem(int position) {
            // TODO Auto-generated method stub
            return parameterList.get(position);
        }

        @Override
        public long getItemId(int arg0) {
            // TODO Auto-generated method stub
            return arg0;
        }

        @SuppressLint("ViewHolder")
        @Override
        public View getView(int position, View convertView, ViewGroup parent) {

            LayoutInflater inflater = (LayoutInflater) context
                    .getSystemService(Context.LAYOUT_INFLATER_SERVICE);
            View view = inflater.inflate(R.layout.listdatahistory, parent, false);

            float[] avgTemp = new float[24];

            for (int i = 0; i < 24; i++) {
                int occurenece = 0;
                float totaltemp = 0;
                for (int j = 0; j < parameterList.size(); j++) {
                    int time = ConvertData.convertTime(parameterList.get(j)
                            .getTime());
                    if (time == i) {
                        totaltemp += parameterList.get(j).getTemp();
                        occurenece++;
                    }
                    avgTemp[i] = (totaltemp / occurenece);
                    Log.d("temp", String.valueOf(totaltemp));
                    Log.d("occ", String.valueOf(occurenece));
                }

            }

            TextView temp = (TextView) view.findViewById(R.id.tempList);
            temp.setText("" + avgTemp);

            TextView bat = (TextView) view.findViewById(R.id.batList);
            bat.setText("" + parameterList.get(position).getDate());

            return view;
        }

    }