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Java Java Data Structures Exploring the Java Collection Framework Maps

Jan Willmann
Jan Willmann
4,387 Points
Posted by Jan Willmann
Jan Willmann
4,387 Points

Why do we need this line of code?

It's the code challange: Maps

Can someone explain me why we need that line of code:

categoryCounts.put(blogPost.getCategory(),counter);

 public Map<String, Integer> getCategoryCounts() {
    Map<String, Integer> categoryCounts = new HashMap<>();

    for (BlogPost blogPost : mPosts) {
      Integer counter = categoryCounts.get(blogPost.getCategory());
      if (counter == null) {
        counter = new Integer(0);
        categoryCounts.put(blogPost.getCategory(), counter);

      }
      counter++;
      categoryCounts.put(blogPost.getCategory(), counter);  // Why do we need this line of code? 
    }
  return categoryCounts;
  }

When is worked here with just using the object reffernce? 

 Map<String, List<Treet>> treetsByAuthor = new HashMap<String, List<Treet>>();

    for (Treet treet : treets) {
      List<Treet> authoredTreets = treetsByAuthor.get(treet.getAuthor());
      if (authoredTreets == null) {
        authoredTreets = new ArrayList<Treet>();
        treetsByAuthor.put(treet.getAuthor(), authoredTreets);
      }
      authoredTreets.add(treet);
    }

Doesn't it work, because "counter" is just a primitive type and "List<>" is an object?