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list iterator

Posted on 2008-06-23
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Last Modified: 2010-03-30
Hi,

I use iterators with maps pretty often like:

    for (Map.Entry<Integer, String> it: mylist.entrySet()) {
       it.getValue().toString();
    }

how do you do the same with an ArrayList?

Thanks
0
Comment
Question by:DJ_AM_Juicebox
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6 Comments
 
LVL 86

Accepted Solution

by:
CEHJ earned 1000 total points
ID: 21850253
for (T t : someList)

(where 'T' is the type)
0
 
LVL 92

Expert Comment

by:objects
ID: 21851250
Heres an example:

ArrayList<String> list = new ArrayList<String>();

for (String s : list}
{
    System.out.println(s);
}

0
 

Author Comment

by:DJ_AM_Juicebox
ID: 21862528
Quick question on that, consider:

public class Test
{
    ArrayList<Car> m_cars;

    public ArrayList<Car> getCars()
    {
        return m_cars;
    }
}

public static void main()
{
    Test test = new Test();

    for (Car car : test.getCars())
    {
         ....
    }
}

every time an iteration of the for-loop is done, does it need to call getCars() for any reason? I'm comparing that to:

    for (int i = 0; i < test.getCars().size(); i++) {
          ...
    }

where it would have to call getCars() every iteration.

Thanks
0
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LVL 92

Assisted Solution

by:objects
objects earned 1000 total points
ID: 21862560
no it wouldn't (it would use iterator)

>     public ArrayList<Car> getCars()

on a side note, making it return List instead of ArrayList is generally abetter idea.
Allows you to change the List implementation used in your class in the future without affecting users of the class.

    public List<Car> getCars()

0
 

Author Comment

by:DJ_AM_Juicebox
ID: 21862574
ok thanks
0
 
LVL 86

Expert Comment

by:CEHJ
ID: 21864147
:-)
0

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