Difference between next() and hasNext() methods in Java collections

Program:

import java.util.*;

public class ListExample {
  public static void main(String[] args) {
    //creating a list of integers
    List < Integer > int_list = new ArrayList < Integer > ();

    //adding some of the elements
    int_list.add(10);
    int_list.add(20);
    int_list.add(30);
    int_list.add(40);
    int_list.add(50);

    //printing elements
    System.out.println("List elements are...");
    //creating iterator
    Iterator < Integer > it = int_list.iterator();

    while (it.hasNext()) {
      System.out.println(it.next());
    }
  }
};

Output

List elements are...
10
20
30
40
50