Good post! Your Java 8 version is more expressive and also works, but your lambda has a side effect, which is not recommended. You are changing the state of the pairs list inside the lambda. My version computes the partial results and collects them into a list at the end.

Overall the main lines are these:

mapOfLists.forEach((k, list) -> list.forEach(e -> pairs.add(new Pair(k, e))));
System.out.println(pairs);


final List<String> list = new ArrayList() {{
add("Hello");
}};
final Iterator<String> iterator = list.iterator();
System.out.println(iterator.next());
list.add("World");
System.out.println(list.get( 1 ));
System.exit( 0 );
System.out.println(iterator.next());



final List<String> list = new ArrayList() {{
add("Hello");
}};
final Iterator<String> iterator = list.iterator();
System.out.println(iterator.next());
list.add("World");
System.out.println(list.get( 1 ));
try
{
System.out.println(iterator.next());
} catch ( Exception e )
{
}


def list = [5, 6, 7, 8]

def map = [name:”Gromit”, likes:”cheese”, id:1234]

🙂