Error: cannot resolve symbol

This error occurs in the following code:

public class example {

public static void main(String[] args) {

ArrayList list = new ArrayList();

for (int i = 0; i < 4; i++)
{
list.add (new Integer (i*i));
System.out.println (list.get(i));
}

}
}

Does anyone have any suggestions how to print the elements in the arraylist? The error I get is

"cannot resolve symbol class ArrayList"

TIA

Try adding in an import directive. import java.util.*;

This code uses java 5's(jdk1.5.0) new feature called generics. They are supposed to increase type safety by only allowing the <type> or it's subtypes to be stored within the Collection. Also casting should not be needed when grabbing an element out of a collection to be stored in ref variable of the <type>. But for some reason a cast is still needed ie. Integer integer = (Integer)i.next(); even though the Collection is specified only to hold <Integer> types. If <type> is added to the Iterator then the cast is not needed.

Code:

---

for(Iterator<Integer> i = list.iterator();i.hasNext();){
  Integer integer = i.next();  then the cast is not needed. 
 }

---

Code:

---

  import java.util.*;

  List<Integer> list = new ArrayList<Integer>();
    int element = 0;

  while(true){
    list.add(new Integer(element));
    element = element + 1; // add 4 elements
    if(element == 4) break;
  }

    for(Iterator i = list.iterator();i.hasNext();){
      Integer integer = (Integer)i.next(); 
      System.out.println(integer);
  }

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Quote:

---

But for some reason a cast is still needed ie. Integer integer = (Integer)i.next(); even though the Collection is specified only to hold <Integer> types.

---

The Iterator doesn't know where it came from. That's the weird thing about Java's generics. If the iterator itself doesn't have the type specified, then it's just a normal iterator over Objects.

Quote:

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Posted by CornedBee

The Iterator doesn't know where it came from. That's the weird thing about Java's generics. If the iterator itself doesn't have the type specified, then it's just a normal iterator over Objects.

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Yeah it's kinda odd how the language dosen't force the deveopler to specify a type when declaring an Iterator, but then again i guess it's not needed. I don't really see any added benefit of type saftey by having to do that.

The problem is that the system cannot determine what type it's supposed to be. An Iterator is just an Iterator. An Iterator<Byte> is what does the type checking.