Question

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(question in green) What does it mean for an inner class object to be a reference of an outer class? what can you use an iterator on but not for each loop on?

Answer 1

Inner class means one class which is a member of another class. Inner classes has access to all members e.g. static and non-static variables and methods, including private of its outer class and may refer to them directly in the same way that other non-static members of the outer class do.

For example

class Outer {
  
class Inner {
public void display() {
System.out.println("This is inner class method");
}
}
}
public class Main {
public static void main(String[] args) {

   new Outer().new Inner().display();

}
}

For Iterator and For each loop

If you want to modify the Collection then use iterator because you can't do it with for each loop

And it will throw a ConcurrentModificationException

If you can modify or delete an item in collection by Iterator

Please let me know if you have any doubt or modify the answer, Thanks :)