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Thread: collection problem

  1. #1
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    Default collection problem

    Hi all,

    I am new to this forum.

    I am using this code but it is not giving any out put

    import java.util.*;
    public class ListiteratorDemo {

    public static void main(String args[])
    {
    ArrayList ob = new ArrayList();
    ob.add(4);
    ob.add(5);
    ob.add(6);
    ob.add(7);
    ListIterator lit = ob.listIterator();
    while(lit.hasPrevious())
    {
    System.out.println(lit.previous());
    }
    }
    }





    please help me!!!!!!!


  2. #2
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    Default Re: collection problem

    Moved to Collections and Generics

    See the API on ListIterator (Java Platform SE 6) Iterator's move from start to end...and prior to ever calling next there is no previous element

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    Default Re: collection problem

    previous is there man . why it is not showing my elements ?

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    Default Re: collection problem

    Hello freakycoder!
    Quote Originally Posted by freakycoder View Post
    previous is there man . why it is not showing my elements ?
    From the API:hasPrevious() Returns true if this list iterator has more elements when traversing the list in the reverse direction. (In other words, returns true if previous would return an element rather than throwing an exception.)

    Therefore if you print lit.previous() before the loop you will see if there is a previous element in your list.

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    Default Re: collection problem

    Not getting

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    Default Re: collection problem

    Quote Originally Posted by freakycoder View Post
    Not getting
    Did you put
    System.out.println(lit.previous());
    before the while loop in your code?
    You don't get what is printed from the above statement?

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    Default Re: collection problem

    No , but i but it there it will show NoSuchElementException and putting it as show above it show no out put just blank console

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    Default Re: collection problem

    To see what the code is doing, printout the value of the condition used in the while() statement before executing the while statement. That will show you why the while is not executing.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: collection problem

    System.out.println(lit.hasPrevious()); it is printing false . what its mean

  10. #10
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    Default Re: collection problem

    The while loop will never execute.

    Add this just before the println statement you just added:
          lit.next(); lit.next(); //<<<< Move 2 slots to make for previous
    Last edited by Norm; June 26th, 2012 at 11:47 AM.
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    Default Re: collection problem

    yeah it is working but is it compulsory to write next() method before each of previous method?

  12. #12
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    Default Re: collection problem

    If you are at the beginning of a list, what would be the previous element in the list?
    Can you give me an example?
     1st   2nd     3rd
    ^    ^       ^       ^
    If you are before 1st what would be the previous element?
    Last edited by Norm; June 26th, 2012 at 12:02 PM.
    If you don't understand my answer, don't ignore it, ask a question.

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    Default Re: collection problem

    Now its working but I want to know one more thing that is it compulsory to write next method before each of previous() method ?

  14. #14
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    Default Re: collection problem

    See post #12
    If you don't understand my answer, don't ignore it, ask a question.

  15. The Following User Says Thank You to Norm For This Useful Post:

    freakycoder (June 27th, 2012)

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