### Question:
DefaultHttpTransport implements HttpTransport { public static DefaultHttpTransport getInstance( ServiceCombSSLProperties serviceCombSSLProperties) { if (null == DEFAULT_HTTP_TRANSPORT) { synchronized (DefaultHttpTransport.class) { if (null == DEFAULT_HTTP_TRANSPORT) { DEFAULT_HTTP_TRANSPORT = new DefaultHttpTransport(serviceCombSSLProperties); } } } return DEFAULT_HTTP_TRANSPORT; } private  DefaultHttpTransport(ServiceCombSSLProperties serviceCombSSLProperties); static DefaultHttpTransport getInstance(
      ServiceCombSSLProperties serviceCombSSLProperties); @Override Response execute(HttpUriRequest httpRequest); @Override Response sendGetRequest(String url); Response sendGetRequest(String url, Map<String, String> headers); @Override Response sendPutRequest(String url, HttpEntity httpEntity); @Override Response sendPostRequest(String url, HttpEntity httpEntity); @Override Response sendDeleteRequest(String url); @Override void setServiceCombAkSkProperties(ServiceCombAkSkProperties serviceCombAkSkProperties);  }### Answer:
@Test public void getInstance() { DefaultHttpTransport instance = DefaultHttpTransport.getInstance(null); assertNotNull(instance); DefaultHttpTransport instance2 = DefaultHttpTransport.getInstance(null); assertEquals(instance, instance2); }