sszuev commented on code in PR #1994:
URL: https://github.com/apache/jena/pull/1994#discussion_r1308403762
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jena-core/src/main/java/org/apache/jena/graph/GraphMemFactory.java:
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@@ -30,8 +30,17 @@
/**
* A factory class for creating memory Graphs.
* <p>
- * Apache Jena is migrating to term semantics graph for consistency across all
in-memory and persistent storage graphs
- *
+ * Apache Jena is migrating to term semantics graph for consistency across all
in-memory and persistent storage graphs.
+ * <p>
+ * All the graphs that this factory creates are <strong>not
thread-safe</strong>.
+ * Note that if the memory Graph is structurally modified at any time after
+ * the iterator has been created by any of the {@code find*} or {@code
stream*} methods, the iterator may throw
+ * a {@link java.util.ConcurrentModificationException
ConcurrentModificationException}
+ * if continued with it after this modification.
+ * This may happen even if the queried data does not relate directly to
modified data
+ * (i.e. when triple search pattern does not match added or deleted triple).
+ * The good practice is to explicitly close iterators immediately after a read
operation or
+ * use terminate operations such as {@link ExtendedIterator#toList()}.
Review Comment:
It looks like I still don't quite understand the functional difference
between `ExtendedIterator` and `Stream`.
Both closeable, both have terminal and intrermediate operations (e.g.
intermediate: `ExtendedIterator.filterKeep`, `Stream.filter`), both can be
exhausted or not), both lazy.
What am I missing out on?
The only functional difference I see - we can call `Iter.findFirst` several
times, for `Stream.findFirst` it is not possible. But as I mention above, the
method `ExternalIterator.findFirst` with close, would be more convenient than
`Iter.findFirst` without close. Anyway this difference is not so important
(IMO), maybe considered as a feature, which makes `ExtendedIterator` more
suitable choice in some cases. And `Stream` is more heavy and complicated.
`AutoCloseable` is not required to be closed, it is also "good practice",
but in Java we can use `try-with-resources` to make our code safer more
elegant.
Also, switching to `AutoCloseable` will not break user code.
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