HTTP Response header - how to retrieve particular value from the HTTP Response Header java -

passing secret key in rest service , check response code if response code = 200 collect http response header

if (responsecode == 200) {             bufferreader = new bufferedreader(new inputstreamreader((connection.getinputstream())));      string output;      stringbuilder builder = new stringbuilder();      system.out.println("output server .... \n");      while ((output = bufferreader.readline()) != null)            builder.append(output);      system.out.println(builder.tostring());      }     

output

{ "issued_at" : "1470049186841",    "scope" : "core",  "status" : "approved",   "api_product_list" : "[prod]",   "expires_in" : "1199",   "token_type" : "bearertoken",  "access_token" : "mx1glcbhipxsegi7yrbar0kvs03j",    "refresh_token_expires_in" : "0",  "refresh_count" : "0"} 

from output want pick access_token value

note: below salesforce code, want convert java

 map<string,string> responsemap= new map<string,string>())json.deserialize(res.getbody(),map<string,string>.class);             return responsemap.get("access_token"); 

updated: gson api code below

gson gson = new gson();             map<string, object> map78 = new hashmap<>();             map78 = (map<string, object>) gson.fromjson(output, map.getclass()); 

but getting null value

with of marcel getting answer using gson

bufferedreader br = null;         string output = null;         map<string, object> responsetoken = new hashmap<>();         if (responsecode == 200) {             br = new bufferedreader(new inputstreamreader((connection.getinputstream())));             stringbuilder builder = new stringbuilder();             while ((output = br.readline()) != null) {                 builder.append(output);                            }             gson gson = new gson();                       responsetoken = (map<string, object>) gson.fromjson(builder.tostring(), responsetoken.getclass());             system.out.println("from map" + responsetoken);         }         system.out.println ("access token key "+responsetoken.get("access_token"));