PowerMockito.doReturn returns null

This is my class under test:

public class A {

public Integer callMethod(){
  return someMethod();
}


private Integer someMethod(){
  //Some Code
  HttpPost httpPost = new HttpPost(oAuthMessage.URL);
  //Some Code
  HttpClient httpClient = new DefaultHttpClient();
  HttpResponse httpResponse = httpClient.execute(httpPost); ------1
  Integer code = httpResponse.getStatusLine().getStatusCode(); ---2
  return code;
}

Now I want to mock the line 1 & 2 & return a mock HttpResponse & code.

I have tried this but failed:

@RunWith(PowerMockRunner.class)
@PowerMockIgnore("javax.crypto.*")
public class TestA {

//Spying some things here & Injecting them

@Test
public void testA() {


   DefaultHttpClient defaultHttpClientMock = PowerMockito.mock(DefaultHttpClient.class);
   HttpResponse httpResponse = PowerMockito.mock(HttpResponse.class, RETURNS_DEEP_STUBS);
   HttpClient httpClient = PowerMockito.mock(HttpClient.class);
   //HttpResponse httpResponseMock    PowerMockito.mock(HttpResponse.class);
   HttpPost httpPost = PowerMockito.mock(HttpPost.class);
   PowerMockito.whenNew(DefaultHttpClient.class).withNoArguments().thenReturn(defaultHttpClientMock);
   PowerMockito.doReturn(httpResponse).when(httpClient).execute(httpPost);      //Returns null. It never returns httpResponse.
   PowerMockito.when(httpResponse.getStatusLine().getStatusCode()).thenReturn(anyInt());
   //call the method
}

PowerMockito.doReturn(httpResponse).when(httpClient).execute(httpPost) always returns null. I want it to return the mock object of HttpResponse. I have read other posts related to this error but not sure what to do in my case. Can anyone help?