One of the common interview question is “What is difference between ArrayList and LinkedList”.Before we actually see differences,let me give you brief introduction of both.
ArrayList
- ArrayList is implementation of list interface.
- ArrayList is not synchonized(so not thread safe)
- ArrayList is implemented using array as internal data structure.It can be dynamically resized .
LinkedList
- LinkedList is implementation of list and deque interface.
- LinkedList is not synchronized
- LinkedList is implemented using doubly linked list as internal data structure.
ArrayList vs LinkedList:
|
Parameter
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ArrayList
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LinkedList
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|---|---|---|
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Internal data structure
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It uses dynamic array to store elements internally
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It uses doubly Linked List to store elements internally
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Manipulation
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If  We need to insert or delete element in ArrayList, it may take O(n), as it internally uses array and we may have to shift elements in case of insertion or deletion
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If  We need to insert or delete element in LinkedList, it will take O(1), as it internally uses doubly LinkedList
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Search
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Search is faster in ArrayList as uses array internally which is index based. So here time complexity is O(1)
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Search is slower in LinkedList as uses doubly Linked List internally So here time complexity is O(n)
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Interfaces
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ArrayList implements List interface only, So it can be used as List only
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LinkedList implements List,Deque interfaces, so it can be used as List,Stack or Queue
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When to use ArrayList or LinkedList?
It actually depends on our need.
- If we have more insertion or deletion then we should use LinkedList.
- If we have less insertion or deletion and more search operations then we should use ArrayList.
Please go through  core java interview questions for more interview questions.
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