How Do I Iterate Generic List Using For Each Type For Loop
collections, foreach, generic-list, java
Solution
It's not considered as an instance of `java.lang.Iterable` because it does not implement the interface `java.lang.Iterable`. As simple as that. Change its declaration to
public class GList<T> implements Iterable<T>
and you'll be ale to use the foreach loop with it. But since `list` is an instance of `GList<InnerList>`, and since a `GList<InnerList>` contains instances of `InnerList` (at least, I guess so), the loop should be:
for (InnerList innerList : list) {
...
}
Problem
I have been given an assignment to create a list of lists where I should be able to iterate through the lists using the 'for each' type of 'for' loop, versus building a constructor for Iterator. The problem is that when I the code below, I get the error msg "Can only iterate over an array or an instance of java.lang.Iterable". Here is the code: ``` public static void main(String[] args) { GList<InnerList> list = new GList<InnerList>(); GList<InnerList> numList = new GList<InnerList>(); InnerList lst = new InnerList (); Scanner sc = new Scanner(System.in); String answer; while (true){ System.out.println ("Do you want to create a list (y/n)? "); answer = sc.next(); if (answer.equals("y")){ System.out.println("Enter the name of the list: "); answer = sc.next(); lst.setName(answer); if (list.isEmpty()== true){ list.insertFirstItem(lst); } else { list.insertNext(lst); } } while (true){ System.out.println("Do you want to enter a number (y/n)?"); answer = sc.next(); if (answer.equals("y")){ System.out.println("Enter Number: "); answer = sc.next(); try { int num1 = Integer.parseInt(answer); lst.setInner(num1); if (list.isEmpty() == true){ list.insertFirstItem(lst); } else { list.insertNext(lst); } } catch (NumberFormatException e){ System.out.println("You must enter an number! " + e); sc.close(); } } return; } } for (GList<InnerList> ilName : list){ //here are my error msgs. I also tried replacing GList<InnerList> with 'InnerList' and String. for(GList<InnerList> ilInts : list){ System.out.println(ilName); System.out.println(ilInts); } } } ``` Can someone help me understand why GList is not considered an instance of java.lang.iterable when collections should be iterable? Thank you.