Iterator: sync post code blocks to repo exactly, Java 25, add H6 file labels and README mapping, fix stale console output

03-behavioral/iterator/README.md

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+# Iterator Design Pattern — Java Example
+
+**Pattern:** Behavioral → Iterator
+**Article:** https://ankurm.com/iterator-design-pattern-java/
+
+## What this example shows
+
+A `BookShelf` stores `Book` objects in an internal `ArrayList` but never exposes it. Callers only see the `BookIterator` interface (`hasNext()`/`next()`). `BookShelf` hands out two different concrete iterators: `ForwardIterator` walks every book in order, and `DecadeIterator` filters to only books published in a given decade, computing the next match lazily as `advance()` is called. `Main` exercises both iterators, then prints a line noting that `java.util.Iterator`/for-each work the same way under the hood.
+
+## How to run
+
+```bash
+javac iterator/*.java -d out/iterator
+java -cp out/iterator iterator.Main
+```
+
+Requires Java 25.
+
+## Post Section ↔ File Mapping
+
+| Post Section | File(s) |
+|---|---|
+| Custom Iterator Implementation — the Iterator interface | `BookIterator.java` |
+| Custom Iterator Implementation — the element type | `Book.java` |
+| Custom Iterator Implementation — the Aggregate (BookShelf, ForwardIterator, DecadeIterator) | `BookShelf.java` |
+| Custom Iterator Implementation — wiring it together | `Main.java` |
+
+Note: the "How Java's For-Each Loop Uses Iterator" snippet (`Iterable<Book>` example) is illustrative only — it is not part of this repository's runnable example.
+
+Article: https://ankurm.com/iterator-design-pattern-java/
+All patterns: https://ankurm.com/design-patterns-java/