generics inside collection

[Dieter]

Heyaa,

Today i saw generics and collections at school.
But i'm trying to combine those tgetter.

but i don't know where or how to give values to it in thi situation.

got this code so far..

 import java.util.*;

/**
 *
 * @author Dieter
 */
public static void main(String[] args) {

        DuoArraylist<Integer> n1 = new DuoArraylist<Integer>(3,5);

        List <DuoArraylist<Integer>> ex = new ArrayList<DuoArraylist<Integer>>();
         ex.add(null);
         ex.add(n1);

         System.out.println(ex);
    }

Now for the DuoArraylist class...

public class DuoArraylist <E extends Number> {

    private E arrayItem1;
    private E arrayItem2;
    

    public DuoArraylist(E arrayItem1, E arrayItem2) {
        this.arrayItem1 = arrayItem1;
        this.arrayItem2 = arrayItem2;
        
    }

    public E getArrayItem1() {
        return arrayItem1;
    }

    public void setArrayItem1(E arrayItem1) {
        this.arrayItem1 = arrayItem1;
    }

    public E getArrayItem2() {
        return arrayItem2;
    }

    public void setArrayItem2(E arrayItem2) {
        this.arrayItem2 = arrayItem2;
    }

   
    
   

}

Tips or suggestions are allways welcome :)

Thanks in advance,

Dieter

[r035198x]

What's the problem? You didn't really specify a question.
What is code doing vs what it should be doing?

[Dieter]

i want to display the values i give to DuoArraylist in the Arraylist

but it displays

run:
[null, arraylistapp.DuoArraylist@19821f]
BUILD SUCCESSFUL (total time: 0 seconds)

[RamyaSivakanth]

Hi,
As per the code u have written,It has printed perfectly.

You have added null and DuoArrayList object.

My question is why u added null at first index?

To retreive the DuoArrayList related values,do like this below.


DuoArraylist obj = (DuoArraylist)ex.get(1);

After getting the object try to call the getter method to print ur inputted values.

[r035198x]

...

To retreive the DuoArrayList related values,do like this below.


DuoArraylist obj = (DuoArraylist)ex.get(1);

..

Don't do any of that. Otherwise there is no point in using the generics in the first place.

Rather do

DuoArraylist<Integer>  duo= ex.get(1);

[RamyaSivakanth]

Hi ro35198x,
U are right.Great catch!!!. forgotten when I type....

Hi Dieter,
without typecasting try to retreive DuoArraylist<Integer> duo= ex.get(1); like r0... told.

-Regards
Ramya

[emceenugget]

isn't "array list" a bit of a misnomer, considering you don't implement anything with an array?

anyways, your problem is that you're printing out a list containing lists (DuoArraylist to be exact). to print the items in the DuoArraylists, you have to do that separately.

you're just mixing up your lists... draw it out and it'll make sense

[Dieter]

the null value is someting i forgot to get out when i was just writing an arraylist with different values in the previous exe.

duo= ex.get(1);

where should i put that in code? in or out the list?

ah well i will try it tmorrow if i got the time.
Thanks alot to you all for making it more clear to me now :)

All the best,

Dieter