how can I implement iterable for LinkedList<LinkedList<obj>>

Question

I have created :

LinkedList<LinkedList<Object>>

I know how to implement Iterable for regular linked list in order to iterate.

However, how can I implement Iterable in order to be able to iterate over my collection when it is

LinkedList<LinkedList<Object>> ? 

Answer 1

Iterable is a generic interface. Since you want to iterate over a LinkedList<LinkedList<Object>>, you can implement the interface with the type parameter set to LinkedList<Object>.

Sample runnable class:

public class IterableClass implements Iterable<LinkedList<Object>>{
    LinkedList<LinkedList <Object>> l = new LinkedList<LinkedList<Object>>();


    public IterableClass() {
        super();
        LinkedList<Object> a = new LinkedList<Object>();
        a.add("a1");
        a.add("a2");
        LinkedList<Object> b = new LinkedList<Object>();
        b.add("b1");
        b.add("b2");
        l.add(a);
        l.add(b);
    }

    public static void main(String[] args) {
        IterableClass iterableObject = new IterableClass();
        for(Iterator<LinkedList<Object>> it = iterableObject.iterator(); it.hasNext(); ) {
            LinkedList<Object> list = it.next();
            for (Iterator<Object> iterator = list.iterator(); iterator.hasNext();) {
                Object object = iterator.next();
                System.out.println(object);
            }
        }
    }

    @Override
    public Iterator<LinkedList<Object>> iterator() {
        return l.iterator();
    }

}

Output:

a1
a2
b1
b2

Answer 2

Like here:

Iterator<LinkedList <Object>> iterator = yourList.iterator();
while (iterator.hasNext()) {
    LinkedList<Object> embededList=iterator.next();
    Iterator<Object> embededIterator= embededList.iterator();
    while(embededIterator.hasNext()){
       System.out.println(embededIterator.next());
    }
}

edited.