Arraylist values not coming in a HashMap

Question

I have a HashMap as below:

public static HashMap submitService(HashMap inputMap) throws Exception
    {
        //code....

        ArrayList<String> allIdsList = (ArrayList<String>) inputMap.get("Result_List");
        // System.out.println("Result List: " + allIdsList); prints the arraylist (e.g. [2, 21, 6, 3]

        for(int i=0;i<allIdsList.size();i++)
            {
                System.out.println(" values: " + (String)allIdsList.get(i));
            }
    }

the arraylist is printing in the console(I tried it only to see if the list is not empty). But for (String)allIdsList.get(i) inside the for loop following error message is coming

java.lang.Long cannot be cast to java.lang.String

Would really appreciate someone's help.

why are you casting to string? You initialized the arraylist with <String>. Therefore the get method should return a String, without the need to cast! Same goes for the hashmap. Try to init it with HashMap<String,ArrayList<String>> inputMap — Steffen Nieuwenhoven
– Steffen Nieuwenhoven, Commented Jun 16, 2013 at 9:58
Even if it works, think about waht you are doing (even if only for later reference). your getting one element of a arraylist, filled with strings, and you need to cast it to string to work, because appearently it contains long and not strings...Something is wrong there, probably with the argument in the method call. Just be careful this doesn't bite you in the a... later on :) — Steffen Nieuwenhoven
– Steffen Nieuwenhoven, Commented Jun 16, 2013 at 10:59

Aneeq Anwar · Accepted Answer · 2013-06-16 10:54:54Z

1

Make sure HashMap is of type HashMap<String,ArrayList<String>>

answered Jun 16, 2013 at 10:54

Aneeq Anwar

1,3328 silver badges20 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

ajay.patel · Accepted Answer · 2013-06-16 10:09:12Z

0

Replace: public static submitService(HashMap<'String,ArrayList<'String>> inputMap) throws Exception

Looking at the exception, its sure that the parameter passed does not have arraylist of string.Looks like it might be ArrayList<'Object>(with long value present in the list which eventually is casted in String) or Arraylist<'Long>.

answered Jun 16, 2013 at 10:09

ajay.patel

1,96712 silver badges15 bronze badges

1 Comment

ajay.patel Over a year ago

HashMap<String,ArrayList<String>>, there is some problem with editor.

Steffen Nieuwenhoven · Accepted Answer · 2013-06-16 10:09:19Z

0

Try this:

public static HashMap<String,ArrayList<String>> submitService(HashMap<String,ArrayList<String>> inputMap) throws Exception
{
    //code....

    ArrayList<String> allIdsList = inputMap.get("Result_List");
            for(int i=0;i<allIdsList.size();i++)
        {
            System.out.println(" values: " + allIdsList.get(i));
        }
}

answered Jun 16, 2013 at 10:09

Steffen Nieuwenhoven

5258 silver badges22 bronze badges

Comments

Mattias Buelens · Accepted Answer · 2013-06-16 11:05:53Z

Where is this inputMap coming from? By the looks of it, its values are not of type ArrayList<String> but something like ArrayList<Object> or even ArrayList<Long>. The problem seems to be somewhere outside your posted snippet.

Since you're working with raw types in this method, the compiler won't complain (although it should warn you about using raw types). However, the VM will throw a ClassCastException where the cast fails - that's what you're seeing.

Try strengthening your signature by only accepting HashMap<String, ArrayList<String>> as inputMap. That way, you can get rid of those awful casts, as you now get compile time type checks. In the best case, this will give the compiler enough information to point out where you're calling this method with an incorrectly typed inputMap. You should then be able to easily fix the error merely by following the compiler's instructions. If that doesn't work, you're probably using raw types in your calls as well and you'll need to dig down the stack trace to fix those.

Nagasitaram Thigulla · Accepted Answer · 2024-07-11 12:06:11Z

0

It looks like allIdsList is of type ArrayList<Long> but you are using ArrayList<String>.

You can change the type of allIdsList to either ArrayList<Long> or remove the generic and use ArrayList.

answered Jul 11, 2024 at 12:06

Nagasitaram Thigulla

1881 silver badge9 bronze badges

Collectives™ on Stack Overflow

Arraylist values not coming in a HashMap

5 Answers 5

Comments

1 Comment

Comments

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

Comments

1 Comment

Comments

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related