Why ArrayList hash map assigns same values to same objects at different positions;

Question

My app calculates distances between cities. At some time, i get an ArrayList hash map of the form:

 [{username=p, startcity=A, finalcity=B}, 
{username=p, startcity=C, finalcity=D}, 
{username=f, , startcity=E, finalcity=D}, 
{username=e, startcity=F, finalcity=L}]

Few lines below, i get ArrayList

[{username=p, startcity=A, finalcity=B},
{username=e, startcity=F, finalcity=L}, 
    {username=p, startcity=C, finalcity=D}, 
    {username=f, , startcity=E, finalcity=D}, 
    {username=e, startcity=F, finalcity=L}]

Note that objects at positions 1 and 4 are exactly the same. Then i try to assign at every object a different number. Problem is that the aforementioned objects are getting every time same value...

Code...

for(n=0;n<5;n++){
ArrayList.get(n).put("n",String.valueof(n));
}
Log.d("ArrayList", ArrayList.toString.....

leads to...

[{username=p, startcity=A, finalcity=B , n=0},
{username=e, startcity=F, finalcity=L,n=4!!!!//here...}, 
    {username=p, startcity=C, finalcity=D,n=2}, 
    {username=f, , startcity=E, finalcity=D,n=3}, 
    {username=e, startcity=F, finalcity=L,n=4}]

So i can't differentiate those two objects. Why; Isn't that weird; Is there a way to do this; Thanks in advance

The code above was a very simple translation of the real problem. Code is to big to post here. But..can it happen regarding to the above simple example; Or i'm dreaming... — Fenia Kechagia
– Fenia Kechagia, Commented Jan 30, 2015 at 11:59

ysfseu · Accepted Answer · 2015-01-30 11:43:34Z

0

Firstly, I don't understand what ArrayList hash map means. ArrayList and HashMap is entirely different. Did you do some transformation?Maybe Something wrong happens when you transform the ArrayList to HashMap.

Secondly, you said "few lines below", I think you should paste that few lines, it's necessary for others to help solve your problems.

I hope you can edit your problem again. More details is necessary for solving this problem.

answered Jan 30, 2015 at 11:43

ysfseu

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3 Comments

Fenia Kechagia Over a year ago

stackoverflow.com/questions/19082712/… stackoverflow.com/questions/20831914/… stackoverflow.com/questions/16544928/… what ArrayList<HashMap<String, String>> means

ysfseu Over a year ago

Eh...1.how do you print the first ArrayList. 2. why is there the item with n = 5 when n<5 in your for loop. I don't think your code can lead to that print.

Fenia Kechagia Over a year ago

sorry...as i said, this was an example. Problem remains

Arslan Sohail · Accepted Answer · 2015-01-30 12:00:52Z

0

ArrayList.get(n)

will get the same object when the value of n will be 4 and will override the same object which is placed when n is 1.

answered Jan 30, 2015 at 12:00

Arslan Sohail

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1 Comment

Fenia Kechagia Over a year ago

Any suggestion to differentiate those two objects;

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