DDSJAVA — Data access from DataReader using java.util.List

Currently the DataReader provides read() and take() methods that return a special type of java.util.ListIterator: Sample.Iterator. The Iterator is not the most convenient way to access data retrieved from the DataReader (e.g. an Iterator can only be traversed once).

Propose to modify all read()/take() operations currently returning an Iterator to let them return a java.util.List. The List is more developer friendly, as it can be traversed multiple times and a List is also an Iterable with the added benefit that it can be used in Java’s “foreach” statement:

List<Sample<TYPE>> data = dataReader.read();

for (Sample<Type> sample : data)

Merge this issue with #16321, which proposes other changes to the read/take overloads.
• Overloads that return a loan should do so in the form of a ListIterator implementation, which will allows multiple forward and backward navigation of elements. The loaned samples should not be returned as a List, as retrieving an iterator from a list would force critical-path memory allocation—in direct contradiction of the low-latency goal of the loaning operations.
• Overloads that return a copy should continue to accept a List to be filled in and should return a reference to the same list for convenience. These overloads will therefore support the “for-each” construct requested by this issue.
Disposition: Merged with issue #16321