How to get the results from multiple servers in a function in Android

Question

I'm installing Hybrid Ranking algorithm for Linked Data Extraction & Context on Android. Documents you can search Google for the keywords above. And now I'm installing semantic similarity between two uri1 and uri2.

Input: two DBpedia URIs

Output: a value representing their similarity

private float similarity(String uri1, String uri2) {
     float wikipedia = wikiS(uri1, uri2);
     float abtract = abtractS(uri1, uri2);
     float google = engineS(uri1, uri2, google);
     float yahoo = engineS(uri1, uri2, yahoo);
     float bing = engineS(uri1, uri2, bing);
     float dilicious = engineS(uri1, uri2, dilicicous);
     return wikipedia + abtract + google + yahoo + bing + dilicious;
}

And with each child function, I have to query data using SPARQL dbpedia, google, yahoo, bing, dilicious using provided API. The results obtained will be calculated to the parser and returns the corresponding float value.

Example for abtractS(uri1, uri2) below:

private float abstractS(String uri1, String uri2, final float wikiS){
    String url = createUrlAbstractS(uri1, uri2);
    StringRequest request = new StringRequest(Request.Method.GET, url, new Response.Listener<String>() {
        @Override
        public void onResponse(String response) {
            float abtractS = 0.0f;
            try {
                JSONObject jsonObject = new JSONObject(response);
                JSONArray data = jsonObject.getJSONObject("results").getJSONArray("bindings");
                if(data.length() == 0){
                    showLogAndToast("No result");
                }else{
                    JSONObject element = data.getJSONObject(0);
                    String label1 = element.getJSONObject("label1").getString("value");
                    String abtract1 = element.getJSONObject("abtract1").getString("value");
                    String label2 = element.getJSONObject("label2").getString("value");
                    String abtract2 = element.getJSONObject("abtract2").getString("value");
                    abtractS = calWordContained(label1, abtract2) + calWordContained(label2, abtract1) + wikiS;
                    //TODO: RESULT ABTRACTS HERE. How next?
                }
            } catch (JSONException e) {
                e.printStackTrace();
            }
        }
    }, new Response.ErrorListener() {
        @Override
        public void onErrorResponse(VolleyError error) {
            Log.d(TAG, error.getMessage());
        }
    });
    AppController.getInstance().addToRequestQueue(request);
    return 0.0f;//HERE: no results
}

private float calWordContained(String label, String abtract){
    if(label.length() == 0 || abtract.length() == 0){
        return 0.0f;
    }
    List<String> words = Arrays.asList(label.split(" "));
    int count = 0;
    float length = words.size();
    for(int i = 0; i < length; i++){
        if(abtract.toLowerCase().contains(words.get(i).toLowerCase())){
            count++;
        }
    }
    return (count/length);
}

public String createUrlAbstractS(String uri1, String uri2){
    private String BASE_URL_DBPEDIA = "http://dbpedia.org/sparql?default-graph-uri=&query=";
    String query = createQueryAbstractS(uri1, uri2);
    String url = "";
    try {
        url = Config.BASE_URL_DBPEDIA + URLEncoder.encode(query, "UTF-8") + Config.RESULT_JSON_TYPE;
    } catch (UnsupportedEncodingException e) {
        e.printStackTrace();
    }
    return url;
}

private String createQueryAbstractS(String uri1, String uri2){
    String query = Config.PREFIX_DBPEDIA + " \n" +
            "prefix dbpedia-owl: <http://dbpedia.org/ontology/>\n" +
            "\n" +
            "\n" +
            "select ?label1, ?label2, ?abtract1, ?abtract2 where\n" +
            "{\n" +
            "  {\n" +
            "     select *\n" +
            "     where{\n" +
            "          <" + uri1 + "> rdfs:label ?label1 ;\n" +
            "                         dbpedia-owl:abstract ?abtract1 .\n" +
            "          FILTER langMatches(lang(?abtract1),'en') . \n" +
            "          FILTER langMatches(lang(?label1),'en') .\n" +
            "     }\n" +
            "  }\n" +
            "\n" +
            "\n" +
            "  {\n" +
            "      select *\n" +
            "      where{\n" +
            "          <" + uri2 + "> rdfs:label ?label2 ;\n" +
            "                         dbpedia-owl:abstract ?abtract2 .\n" +
            "          FILTER langMatches(lang(?label2),'en') . \n" +
            "          FILTER langMatches(lang(?abtract2),'en') .\n" +
            "      }\n" +
            "  }\n" +
            "}";
    return query;
}

but how to do this on, I could not get the results I wanted in the similarity function (uri1, uri2). Therefore it will affect the results in different functions.

So I'm asking is: how can I get all the results of the function Wikis, abtractS, engine (google), engine (bing), engine (yahoo), engine (dilicious) in a simple way Best. I currently do on Android and data load times is very important.

Thank you very much!