content: package com.druk.servicebrowser;
  
  import android.content.Context;
  import androidx.annotation.NonNull;
  import android.text.TextUtils;
  import android.util.Log;
  
  import java.io.BufferedReader;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.InputStreamReader;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.TreeMap;
  
  import io.reactivex.Flowable;
  import io.reactivex.schedulers.Schedulers;
  
  public class RegTypeManager {
  
      private static final  String TAG = "RegTypeManager";
  
      private TreeMap<String, String> mServiceNamesTree;
      private Context mContext;
  
      RegTypeManager(@NonNull Context context) {
          this.mContext = context;
          // Load reg type descriptions as quick as possible on io thread
          Flowable.just("_zigbee-gateway._udp.")
                  .map(this::getRegTypeDescription)
                  .subscribeOn(Schedulers.io())
                  .observeOn(Schedulers.computation())
                  .subscribe();
      }
  
      public List<String> getListRegTypes() {
          if (this.mServiceNamesTree == null){
              return new LinkedList<>();
          }
          return new LinkedList<>(mServiceNamesTree.keySet());
      }
  
      public String getRegTypeDescription(String regType) {
          if (mServiceNamesTree == null){
              synchronized (this) {
                  if (mServiceNamesTree == null) {
                      mServiceNamesTree = new TreeMap<>();
                      try {
                          InputStream is = mContext.getAssets().open("service-names-port-numbers.csv");
                          try {
                              BufferedReader reader = new BufferedReader(new InputStreamReader(is));
                              String line;
                              while ((line = reader.readLine()) != null) {
                                  String[] rowData = line.split(",");
                                  if (rowData.length < 4 || TextUtils.isEmpty(rowData[0]) || TextUtils.isEmpty(rowData[2]) || TextUtils.isEmpty(rowData[3])) {
                                      continue;
                                  }
                                  if (rowData[0].contains(" ") || rowData[2].contains(" ")) {
                                      continue;
                                  }
                                  mServiceNamesTree.put("_" + rowData[0] + "._" + rowData[2] + ".", rowData[3]);
                              }
                          } catch (IOException ex) {
                              // handle exception
                          } finally {
                              try {
                                  is.close();
                              } catch (IOException e) {
                                  Log.e(TAG, "init error: ", e);
                              }
                          }
                      } catch (IOException e) {
                          e.printStackTrace();
                          Log.e(TAG, "service-names-port-numbers.csv reading error: ", e);
                      }
                  }
              }
          }
          return mServiceNamesTree.get(regType);
      }
  
  
  }
  