LinkedHashMap with ArrayList - How to load ArrayList?

Question

I am fairly new to Java and am trying to load a LinkedHashMap that contains an ArrayList of values. I am trying to load the values from a query result from an API based query result (Salesforce).

Here is the error: "Cannot refer to a non-final variable breakdown inside an inner class defined in a different method" - the breakdown variable is underlined in red giving this message, Ive noted the line in concern below.

CODE

public LinkedHashMap<String, ArrayList<String>> sfFundIdsByContact;

    public ArrayList<String> getFundsIDsForContact(Contact aContact)
    {
        QueryResult queryResults = null;
        ArrayList<String> ids = new ArrayList<String>();
        int index = 0;
        Boolean done = false;
        String contactid = aContact.getId();
        String SCCPBId = null;

        if(sfFundIdsByContact == null || sfFundIdsByContact.size() <= 0){

       //Do the Salesforce API CALL and Return the results  
       ...          
       while (! done) 
       {        
        SObject[] records = queryResults.getRecords();

        for ( int i = 0; i < records.length; ++i ) 
            {
                    if(sfFundIdsByContact.containsKey(breakdown.getSalesConnect__Contact__c())){
                        sfFundIdsByContact.get(breakdown.getSalesConnect__Contact__c()).add(breakdown.getId());
                    } else {
//Line below in the add(breakdown.getId() - contains the error
                    sfFundIdsByContact.put(breakdown.getSalesConnect__Contact__c(), new ArrayList<String>() {{ add(breakdown.getId()); }});

        }

    }

All suggestions are appreciated.

Sorry guys - you are too quick ;) - I had some trouble getting the code in the "CODE" section, but it should be good now. — user2774325, Oct 21 '13 at 21:11

Rohit Jain · Accepted Answer · 2013-10-21T21:08:44.243

3

In your else block, instead of:

new ArrayList<String>() {{ add(**breakdown.getId()**); }}

you can use:

new ArrayList<String>(Arrays.asList(breakdown.getId())

or, since you just want a single element ArrayList, you can use Collections.singletonList that avoids the creation of temporary varargs array:

new ArrayList<String>(Collections.singletonList(breakdown.getId())

The { ... } after the new ArrayList<>() creates an anonymous subclass of ArrayList, which is an inner class only. Inside an inner class you cannot access non-final local variables.

edited Oct 21 '13 at 21:08

answered Oct 21 '13 at 21:03

Rohit Jain

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Or `new ArrayList(Collections.singletonList(breakdown.getId())`. This saves the temporary varargs array. – Holger Oct 21 '13 at 21:05
There's no need to use `new ArrayList`, just use `Arrays.asList(breakdown.getId()` (assuming that `getId()` returns a `String`). – Luiggi Mendoza Oct 21 '13 at 21:06
@LuiggiMendoza I guess that would also be fine here. But just to give OP an equivalent code without change in behaviour I wrote that. `asList` returns fixed size list right? – Rohit Jain Oct 21 '13 at 21:07
In HotSpot, `Arrays#asList` simply implements this as `return new ArrayList(T[] array)`, so you end creating an `ArrayList` from another `ArrayList`. – Luiggi Mendoza Oct 21 '13 at 21:08
@Luiggi Mendoza: Then the map´s type `LinkedHashMap>` must be changed to `LinkedHashMap>` – Holger Oct 21 '13 at 21:08
@Holger Of course that is a better option. Will add that. Thanks :) – Rohit Jain Oct 21 '13 at 21:08
@LuiggiMendoza That `ArrayList` is a different one - `java.util.Arrays.ArrayList`. Not the `java.util.ArrayList`. – Rohit Jain Oct 21 '13 at 21:09
@Holger it is not a better option. Note that OP later reuses this list to add more items. – Luiggi Mendoza Oct 21 '13 at 21:10
In cases like this, I would opt for using Guava's Multimap instead. – Luiggi Mendoza Oct 21 '13 at 21:11
@Luiggi Mendoza: Then he cannot remove the `new ArrayList<>(…)`. Both `Arrays.asList` and `Collections.singletonList` have a fixed size. – Holger Oct 21 '13 at 21:11
Because it is a map which value is a `Collection`. Read OP's code one more time. – Luiggi Mendoza Oct 21 '13 at 21:13
@LuiggiMendoza Yeah sorry, I mixed up comments. – Rohit Jain Oct 21 '13 at 21:13
@Downvoter Any legitimate reason for downvote please? – Rohit Jain Oct 21 '13 at 21:14
Just a quick note..The return type of the method is ArrayList and I'll need to keep it that way to minimize code impacts. – user2774325 Oct 21 '13 at 21:14
@user2774325 Both of the above mentioned approach will give you an `ArrayList`. – Rohit Jain Oct 21 '13 at 21:15
Thanks all. Im getting an error for the "Arrays" portion. Looks like the class is importing just java.util.ArrayList and not java.util.Arrays.ArrayList. Im guessing I'll need to update that import. Will that cause issues with the rest of the code that uses ArrayList? – user2774325 Oct 21 '13 at 21:19
@user2774325 You need to `import java.util.Arrays`. – Rohit Jain Oct 21 '13 at 21:19
Ok thanks - and just to clarify that shouldn't cause any issues with the rest of the code using ArrayList in this class? – user2774325 Oct 21 '13 at 21:20
@user2774325 No. That wouldn't. – Rohit Jain Oct 21 '13 at 21:20

score 0 · Answer 2 · edited May 23 '17 at 10:31

You can ease the code by always retrieving the List value in the for loop, then if it is null create a new one and add it to your Map, otherwise add the value to the list.

for (int i = 0; i < records.length; i++) {
    List<String> value = sfFundIdsByContact.get(breakdown.getSalesConnect__Contact__c());
    if (value == null) {
        value = new ArrayList<String>();
        sfFundIdsByContact.put(breakdown.getSalesConnect__Contact__c(), value);
    }
    value.add(breakdown.getId());
}

As a recommendation, change the definition of

LinkedHashMap<String, ArrayList<String>> sfFundIdsByContact

to

Map<String, List<String>> sfFundIdsByContact

Refer to What does it mean to "program to an interface"?

LinkedHashMap with ArrayList - How to load ArrayList?

2 Answers2