Inserting to an ArrayList of LinkedList

Question

Constructor:

array = new ArrayList<LinkedList<String>>(size);

Trying to insert with this line:

array[index].add(value);

It return an error saying "The type of the expression must be an array type but it resolved to ArrayList<\LinkedList<\String>>"

I'm trying to insert a string into a linkedlist node in an array index using the add linkedlist method. Why isn't that line working?

*This is a hashmap implementation btw, an array of linked lists

Michael Markidis · Accepted Answer · 2016-05-22 05:18:11Z

1

You can't access a list like that.

Here's how you can do this:

ArrayList<LinkedList<String>> array = new ArrayList<LinkedList<String>>(size);

// add a bunch of lists
// How many depends on how deep you want the chaining if you are doing    
// this for a hash function.

array.add(new LinkedList<String>());
array.add(new LinkedList<String>());
array.add(new LinkedList<String>());
array.add(new LinkedList<String>());
array.add(new LinkedList<String>());

// Now based on what index you need (e.g. your hash result), you insert into that list.
int index = hashFunction(...);  
array.get(index).add("abc");

edited May 22, 2016 at 5:18

answered May 22, 2016 at 5:02

Michael Markidis

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2 Comments

Jakkie Chan Over a year ago

If I wanted to insert again, and it hashes to another index, wouldn't I have to use another variable name for a linkedList to insert in that index? If I do, then I couldnt have LinkedList list = new LinkedList<String>(); in the insert method since it keeps using the variable name "list"

Michael Markidis Over a year ago

No, you would just get the index of the list you need to insert into, then add to that list. I assume you are trying to do a hash function with chaining? I can add to my answer to show it with multiple lists.

Mureinik · Accepted Answer · 2016-05-22 05:01:51Z

0

Arrays use the [] operator. Other types (such as Lists) can't, and must use methods (such as get) to access their elements:

array.get(index).add(value);

answered May 22, 2016 at 5:01

Mureinik

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