Question

private static void printIterable(Iterable iterable) {

    // ERROR: "Type mismatch: cannot convert from element type Object to Iterable"
    for (Iterable i : iterable) { 
        System.out.println(i);
    }

}

What the compiler is talking about? Its an Iterable, not an Object.

Answer 1

You try to do something for each Iterable inside the iterable. This would only make sense if iterable was an Iterable<? extends Iterable> (i.e. it would iterate over yet other Iterable objects).

But since you didn’t specify a type argument for the argument, you only know that it will iterate over some kind of object (i.e. the base type Object is applicable).

You should try this:

for (Object o : iterable) { 
    System.out.println(o);
}

When read out loud it read as “For each Object o in iterable, print o“. Replacing Object in that sentence with Iterable should illustrate what the problem was.