Solution for Movie Recommender 2019b #63
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| private Hashtable<String, Integer> HashProduct = new Hashtable<String, Integer>(); | ||
| private Hashtable<Integer, String> InvertedHashProduct = new Hashtable<Integer, String>(); | ||
| private Hashtable<String, Integer> HashUser = new Hashtable<String, Integer>(); | ||
| private int users =0, products =0, reviews = 0; |
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always format your code =0 vs = 0
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| public class MovieRecommender { | ||
| private String file; | ||
| private Hashtable<String, Integer> HashProduct = new Hashtable<String, Integer>(); |
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why did you choose Hashtable vs HashMap?
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I was trying different ways of handling bigs amounts of data to see which would give me faster results for the tests, and that's the way I found when working on the solution and thought was the one that would do better, but after doing some research, I understand now that there is nothing in the hashtable that can't be done using hashmap...
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cool, just wanted you to investigate the difference, which is synchronization please research on that
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I actually was reading about that. I also read that Hashtables would be used for thread-safe applications, but now we can use Collections.synchronizedMap() or ConcurrentHash instead.
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| } | ||
| br.close(); |
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I don't like this is not in a finally block. have you heard about try-catch-with-resources? please investigate about it.
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| int userValue = HashUser.get(user); | ||
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| List RecommendedProducts = new ArrayList<String>(); |
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ArrayList has a constructor that receives an initialCapacity why not using it based in recommendations size?
Can you answer what benefit would it bring implementing this suggestion?
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Giving an initial capacity to the ArrayList will reduce the use of memory keeping the size of the array only at whatever we are going to use
| // http://snap.stanford.edu/data/web-Movies.html | ||
| MovieRecommender recommender = new MovieRecommender("/path/to/movies.txt.gz"); | ||
| MovieRecommender recommender = new MovieRecommender("/Users/alonso/Documents/big-data-exercises/movies.txt.gz"); |
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hard coded paths doesn't looks good at all
| if (line.length() >= 0) { | ||
| sp = line.split(" "); | ||
| key = sp[0]; | ||
| if (key.equals("product/productId:")) { |
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key.equals("product/productId:") can produce a null pointer exception,
"product/productId:".equals(key) can't, something to have in mind.
| getData(); | ||
| } | ||
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| public String getData() throws IOException { |
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| while((line = br.readLine()) != null) { | ||
| if (line.length() >= 0) { | ||
| sp = line.split(" "); |
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what if there are no blank spaces in the line being split?
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I would not be able to get the correct values or keys... Fixed
| } | ||
| br.close(); | ||
| bw.close(); | ||
| return null; |
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returning always null will be helpful somehow?
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Changed getData() to private void instead of public String
Solution for Movie Recommender using Mahout in Java.
Alonso Gutierrez. Academy 2019b