Different Between ArrayList, IntArray and Array<Int> [duplicate]

Question

I am new in Java and Kotlin.

Recently when I read a tutorial while learning Kotlin.

I found there are some Array/List confusing me.

What is the different between ArrayList, IntArray and Array<Int>?
When should I use them?

On the java side there is the fixed sized array: int[] (with the primitive type int) and dynamically sized ArrayList<Integer> (with the int wrapper Integer). — Joop Eggen
– Joop Eggen, Commented Jan 17, 2018 at 15:51
This question basically duplicates two other questions: (1) Difference between List and Array types in Kotlin and (2) IntArray vs Array<Int> in Kotlin — hotkey
– hotkey, Commented Jan 17, 2018 at 15:57

Pavneet_Singh · Accepted Answer · 2018-01-17 15:53:49Z

4

Major differences

ArrayList : resizable, Generic (Objects)

IntArray : primitive, fix length, only Int values

Array<Int> : Generic (Objects), fix length

answered Jan 17, 2018 at 15:53

Pavneet_Singh

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Valentin Michalak · Accepted Answer · 2018-01-17 16:01:21Z

3

I see multiples questions inside of your question and i gonna attempt to help you.

First question: What is the difference between `ArrayList` and `List`:

Array is static in size, ArrayList is autoresizable.
ArrayList can not contains primitive types (like int, char, ...), List can.

Second question: What is the difference between `Array<Int>` and `IntArray`

Check this question who respond to this question: IntArray vs Array<Int> in Kotlin

but in summary:

Array<Int> == Integer[] 
IntArray == int[]

That's it !

edited Jan 17, 2018 at 16:01

answered Jan 17, 2018 at 15:55

Valentin Michalak

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hotkey · Accepted Answer · 2018-01-17 15:55:13Z

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This will partially answer your question: Difference between List and Array types in Kotlin

Besides, the difference between IntArray and Array<Int> is the same as between Java int[] and Integer[]: the former stores primitive integers without wrapping them while the latter boxes them into java.lang.Integer objects. Consider IntArray an optimized form of Array<Int> that does not introduce memory and boxing-unboxing overheads.

answered Jan 17, 2018 at 15:55

hotkey

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First question: What is the difference between `ArrayList` and `List`:

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