Mixing Generic and Non-generic Collections pg no 601 K and B

[kiruthigha rajan]

import java.util.*;
public class TestLegacy {
public static void main(String[] args) {
List<Integer> myList = new ArrayList<Integer>();
// type safe collection
myList.add(4);
myList.add(6);
Adder adder = new Adder();
int total = adder.addAll(myList);
// pass it to an untyped argument
System.out.println(total);
}
}
The older, non-generics class we want to use:
import java.util.*;
class Adder {
int addAll(List list) {
// method with a non-generic List argument,
// but assumes (with no guarantee) that it will be Integers
Iterator it = list.iterator();
int total = 0;
while (it.hasNext()) {
[b]int i = ((Integer)it.next()).intValue();[/b]
total += i;
}
return total;
}

Hai im having doubt in this line

int i = ((Integer)it.next()).intValue();

1)why casting is done here and why we have used intValue().

2) Im having doubt in hasNext() execution..here there are two elements.
in the first hasNext() test the value is true and it enters into the loop and it points to the next element.
when again the hasNext() is checked it should return false as there no element after 6.then how it is executed??

please explain in detail the execution of hasNext() in detail thanks in advance

[John Jai]

kiruthigha rajan wrote:1)why casting is done here and why we have used intValue().

Since the List is not generic and contains only of type Object, it is type cast to Integer. The intValue() is a method of the Integer class to get its contained int value.

kiruthigha rajan wrote:in the first hasNext() test the value is true and it enters into the loop and it points to the next element.
when again the hasNext() is checked it should return false as there no element after 6.then how it is executed??

In the first call to hasNext() it checks the List and returns true since 4 will be returned while a call to next() method.
In the second call to hasNext() it again returns true since 6 will be returned on calling next() method.
Only in the third hasNext() call, the while loop condition fails.

Read - intValue method and hasNext method