Question

Use the Law of Demeter to evaluate the coupling in the following code fragments. If a code fragment violates the Law of Demeter, indicate which parts and why. Code fragment #1: String userID; String email; Thread t = new ServerIOThread(userID, email); t.start(); Code fragment #2: HttpClient client = new DefaultHttpClient(); HttpPut httpPut = new HttpPuti...); HttpResponse response = client.execute(httpPut); HttpEntity entity = response.getEntity(); InputStream content = entity.getContent(); True False

Answer 1

Hey, it is a very good problem to be understood. Let's start:

Code fragments are given in the question:

We need to find which part violates the law of Demeter.

For, understanding this let's have a brief introduction of the law of Demeter.

For a Class C and associated methods M, M should interact with the C objects when:

1. C object is referred.

2. M's argument objects are used

3. Instance variable objects of C

4. Objects created by M or methods which M calls.

5. Objects in a global variable.

Finding the problematic code:

Analyzing code fragment 1:

Since userID and email are the data members of the class and this thread is created from there. So, it is not a violation of the law of Demeter.

Rule 1 Applies here and hence this is not a violation.

Analyzing code fragment 2:

These 3 line violates the law of Demeter.

Rule number 4 states that objects created by the methods can execute their methods.

But here response is an object of Httpresponse and it is using the object of HttpClient which is a clear violation of law of Demeter.

A similar case is valid for the entity and content object. the entity is an object of HttpEntity but interacting with the HttpResponse object.

content is an object of InputStream but interacting with the object of the HttpEntity class.

I hope it will help.

Thanks and all the best :)

Please don't forget to thumbs up if it helped you.

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