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Reputation: 1239

Java LinkedList -- Retrieving the index of an Object


I guess this question that would have already been asked here. I searched but could not find anything similar. So here goes --
I have a custom data object Method and Method is as follows --

public Class Method {
List<String> inputParameters;
String resultVariableName;
}

Now i have a LinkedList<Method> which acts as a repository of Method objects.

Given a Method object is there a way in which the correct index of the Method object can be concretely determined.
My question arises from the face that LinkedList class has an indexOf routine but this routine returns the first occurrence of the object but then there is no given that 2 copies of Method object can not reside in the LinkedList(right ?)
Would tagging every Method object as I add it to the LinkedList solve my purpose and if so is there an ideal way to do it ?

EDIT :
Explaining my use case a little further.
My code basically reads a Velocity template top-down and creates Method objects. One Method object is created for every velocity routine encountered. This explains why the same element can be stored at multiple indices in the LinkedList as there is no real restriction on how many number of time a Velocity routine is called or the inputs/results provided to the Velocity routine.

Now, i have a UI component, one JButton per Method object reference in the LinkedList<Method> by using which the user can click and edit the Method object.

Thus i need to know which exact Method object reference to edit in the event that same elements reside twice or more number of times in the LinkedList<Method>

Upvotes: 0

Views: 3027

Answers (4)

Shashank Kadne
Shashank Kadne

Reputation: 8101

"there is not given 2 copies of Method object can not reside in the LinkedList", if this is a scenario, how will you identify which object to retrieve??

In this case, I would suggest you to use a LinkedHashMap, where you can use a Identifier as a key to uniquely identify a Method's object.

Upvotes: 0

bmkorkut
bmkorkut

Reputation: 616

LinkedList does not avoid duplicates, it may have more than one copy.

You can put a logic to avoid multiple instances, extend the linkedlist class and override the add function to check if Method object already exists.

OR

If you want to get all instances of the Method object, you can use a ListIterator and collect all instances of it, and return this collection as a result.

Upvotes: 0

tnunamak
tnunamak

Reputation: 2069

Duplicates are allowed in LinkedList's.

Upvotes: 0

Jon Skeet
Jon Skeet

Reputation: 1499730

What do you mean by the "correct" index in the first place? If the linked list can contain the same element twice or more (and be careful here - the list will only contain a reference to a Method object, not the object itself) then which index would be "correct" in your view?

Of course you can just iterate over the linked list yourself and return all indexes at which a given Method reference occurs, but it's not clear what you're trying to do with it.

Note that indexes aren't often used with linked lists to start with, as obtaining the element at a given index is an O(n) operation.

Upvotes: 2

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