Java.Collections.What is faster ArrayList or LinkedList?

The answer is: it depends on what you’re doing. But generally:

🏎️ ArrayList is faster than LinkedList in most real-world use cases.

Let’s break it down by operations:

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🔍 1. Access by Index (get/set)

Operation	ArrayList	LinkedList
get(index)	✅ O(1) (fast)	❌ O(n) (slow)
set(index)	✅ O(1) (fast)	❌ O(n) (slow)

🏆 Winner: ArrayList

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🔍 2. Add or Remove at End

Operation	ArrayList	LinkedList
add() at end	✅ O(1) amortized	✅ O(1)
removeLast()	✅ O(1)	✅ O(1)

🏆 Tie, but ArrayList might be faster due to lower overhead.

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🔍 3. Add or Remove in the Middle or Beginning

Operation	ArrayList	LinkedList
add(0, element)	❌ O(n) (shift)	✅ O(1)
remove(0)	❌ O(n) (shift)	✅ O(1)
add(index, element)	❌ O(n)	⚠️ O(n) (need to find node first)
remove(index)	❌ O(n)	⚠️ O(n) (same)

So if you’re inserting/removing frequently at the head, LinkedList can be faster.

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🧠 4. Iteration Performance

Aspect	ArrayList	LinkedList
Sequential scan	✅ Fast (good cache locality)	❌ Slower (poor cache locality)

🏆 Winner: ArrayList

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📦 5. Memory Usage

• ArrayList: Just an array + size → low overhead.
• LinkedList: Each node stores data + next + prev → higher overhead.

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✅ When to use ArrayList:

• You need fast random access.
• You’re mainly adding/removing at the end.
• You’re dealing with large data and care about memory.

✅ When to use LinkedList:

• You need to insert/delete at the beginning often.
• You’re implementing a queue or stack.
• You rarely need random access.