Java versus C# asynchronous abstractions

Do you know the difference between the behavior of the two code snippets that answer the question “Java Equivalent of C# async/await?”?

With almost 100K views on Stackoverflow, many developers are still looking for alternatives to Java absence of the well-known async/await idiom found in most programming languages such as Js, C#, Kotlin or Python. Almost two years after the original post, the CCISEL engineer Miguel Gamboa has presented a Java non-blocking alternative to get the body size of an HTTP request response, which is still attracting increasing attention. Nevertheless, although concise and non-blocking this solution still presents a subtle different behavior from C# async/await use case of the original post. Can you guess what is it?

async Task<int> AccessTheWebAsync()
{ 
   HttpClient client = new HttpClient();
   var urlContents = await client.GetStringAsync("http://msdn.microsoft.com");
   return urlContents.Length;
}

CompletableFuture<Integer> AccessTheWebAsync()
{
   return asyncHttpClient()
      .prepareGet("http://msdn.microsoft.com")
      .execute()
      .toCompletableFuture()
      .thenApply(Response::getResponseBody)
      .thenApply(String::length);
}