What happens when you run the following code?

import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

public class Test<T> implements Iterator<T>{   // 1

    private List<T> list = new ArrayList<T>(); // 2

    public void addList(T... ts) {
        Collections.addAll(list, ts);          // 3
    }

    public static void main(String args[]) {
        Test<String> t  = new Test<String>();
        t.addList("Hello world");
        for (String str : t) {                 // 4
            System.out.print(str + " ");
        }
    }

    public Iterator<T> iterator() {
        return list.iterator();
    }

}
Explanation
For successful implementation of the Iterator class you need to implement these methods: hasNext(), next(), remove(). So, there's compilation error in line 1. In for-each loop you can use arrays, collections and classes, which implement Iterable interface, so - compilation error will occur in line 4.
For successful execution you need to change Iterator interface to Iterable

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