code: public boolean readFromDefaultLocations() {
          final File home = new File(System.getProperty("user.home"));
  
          boolean read = false;
          for (String path : new String[] {".ssh/id_rsa", ".ssh/id_dsa", ".ssh/identity"}) {
              final File key = new File(home, path);
              if (!key.exists()) continue;
  
              try {
  
                  readFrom(key);
                  read = true;
              } catch (IOException e) {
  
                  LOGGER.log(FINE, "Failed to load " + key, e);
              } catch (GeneralSecurityException e) {
  
                  LOGGER.log(FINE, "Failed to load " + key, e);
              }
          }
  
          return read;
      }
docs: Read keys from default keyFiles
  
  {@code .ssh/id_rsa}, {@code .ssh/id_dsa} and {@code .ssh/identity}.
  
  @return true if some key was read successfully.