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Java Java Data Structures - Retired Exploring the Java Collection Framework Maps

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?