add elements to specific index in ArrayList or ArrayAdapter

Question

This maybe looks stupid and/or easy question but I couldn't done this.

I'm getting data from database (only). I need get both element and its id at the same time. For example,

+----------------+
|  id | username |
+----------------+
| 1   | user1    |
| 12  | user2    |
| 103 | user3    |
+----------------+

When I populate the ArrayList or ArrayAdapter (or maybe something else), I want to get the both id and username.

I tried to use add(int index, String object) method in ArrayList and insert(String object, int index) method in ArrayAdapter. But the both methods return me same error:

java.lang.IndexOutOfBoundsException: Invalid index 12, size is 1

How can I solve this problem?

Thanks.

can you post the code ??

Preethi
– Preethi

2015-08-08 18:57:36 +00:00
Commented Aug 8, 2015 at 18:57 — Preethi
– Preethi, Commented Aug 8, 2015 at 18:57
I added an answer, something else?

Andrew
– Andrew

2015-08-08 19:21:43 +00:00
Commented Aug 8, 2015 at 19:21 — Andrew
– Andrew, Commented Aug 8, 2015 at 19:21

Community · Accepted Answer · 2017-05-23 11:58:03Z

2

You used the 12 index, who doesn't exist. If you want add an element to the end, you might use this signature:

objectOfArrayList.add(strigObject); // add an element to end

And, you must always check size of array:

int index = 16;
if (objectOfArrayList.size() > index) {
    objectOfArrayList.add(index -1, stringObject); // add an element to position
}

There was performed checking for adding or inserting value to object of ArrayList:

private void rangeCheckForAdd(int index) {
    if (index > size || index < 0)
        throw new IndexOutOfBoundsException(outOfBoundsMsg(index));
}

UPDATE:

If you need a structure "key - value" (the idea proposed by Vitaliy Tsvayer), you'll use map:

// id - user
LinkedHashMap<Integer, String> map = new LinkedHashMap<>();
map.put(1, "user1");
map.put(12, "user2");
map.put(103, "user3");

Answer to question in the comments:

LinkedHashMap<String, Integer> map = new LinkedHashMap<>();
map.put("user", 1);
int id = map.get("user");
System.out.println("id = " + id); // "id = 1"

It will probably be appeared java.lang.NullPointerException in the last example , if key doesn't exist.

edited May 23, 2017 at 11:58

CommunityBot

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answered Aug 8, 2015 at 18:59

Andrew

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4 Comments

Mirjalal Over a year ago

Thanks. But if there's only 3 records, then it'll not add the element? I tried it, but not solved my problem. Sorry for late reply...

Andrew Over a year ago

@MirjalalTalishinski, for these goals used map

Vitaliy Tsvayer Over a year ago

@AndrewTobilko you mean look at tsvayer's answer?

Mirjalal Over a year ago

@AndrewTobilko so, how can I get this key (id) value for specific user ? For example I want to get 12 if I entered user2 ?

Andrew · Accepted Answer · 2015-08-08 20:52:38Z

0

the reason that you are getting ArrayIndexOutOfBound exception is that first you are inserting 1 in index 1. but then directly trying to insert 12. but at that time the size of the list is only 1.

my suggestion, use HashMap.. where you store ids as key and username as value i.e.

Map<String, String> = new HashMap <String, String>();
map.put('1', "name 1");

edited Aug 8, 2015 at 20:52

Andrew

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answered Aug 8, 2015 at 20:02

Sandeep Singh Chhabada

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