Sybex CSG 17 (Q3 Assessment Test)

[Jc Dang]

I'm not sure the exact page because i purchased through the Play Store.  It says page 54-57/1351.

    List<Integer> data = new ArrayList<>();
    IntStream.range(0, 100).parallel().forEach(s -> data.add(s));
    System.out.println(data.size());

Given how pedantic this test is, I don't think the following answer E for Question 3 is sufficient to be true in all cases.

Points to note:
1. This is a lambda with an expression without a body block. data.add(s) vs  {data.add(s);}
These are not legal:

// missing the mutex reference for synchronized and applied to a lambda expression body
s -> synchronized data.add(s)
s -> synchronized { data.add(s); }
// valid synchronized block but not a valid expression body for a lambda
C. s -> synchronized  (data) data.add(s)
D. s -> synchronized (data) { data.add(s); }

2. Assuming we do convert this lambda to one with a body we could add a sync block as follows:

s -> {
      synchronized(data) {
        data.add(s);
      }
}

2. This scenario can still fail if you don't use the same mutex reference object. Example as follows:

public class Main {
  public static void main(String[] args) {
    List<Integer> data = new ArrayList<>();
    IntStream.range(0, 100).parallel().forEach(s -> {
      synchronized((Integer)s) {
        data.add(s);
      }
    });
    System.out.println(data.size());
  }
}

3. Another option would be to leverage the Collections.synchronizedCollection API.

[Jeanne Boyarsky]

I think the spirit of that question is given a proper synchronized block that meets the requirement. I'll make a note to revisit though.