in java, if we store 4 elements in array and array list, is it same at low level in memory OR does it make any difference in order to store elements ?
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in java, if we store 4 elements in array and array list, is it same at low level in memory OR does it make any difference in order to store elements ?
An array is pretty different from a List, even if the list happens to be an ArrayList and internally uses just an array as well.
For the array there exists just the array (for this discussion I’ll ignore the memory the elements will occupy). Thus you have one object in the heap, the array itself.
For the ArrayList, there exists the ArrayList instance and that instance internally has an array. So there are two objects on the heap. Also, while you have exact control over the size of an array you create, the array held by the ArrayList can have any size that is >= number of elements <= Integer.MAX_VALUE.
Coincidentily, ArrayList uses an elements index directly as array index internally, so the order of elements is the same as in a plain array. But thats an implementation detail, and you normally don’t care how a List organizes its data internally (after all the purpose of Lists is to abstract the messy details away).