[Java Application Performance and Memory Management] Chapter 20 – How Lists Work

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ArrayList is internally created as an Array
- As seen from the above screenshot, it is saved in this.elementData array

Initially, the size of the ArrayList is 0 and the elementData length is 0 as well.
- However when the first element is added, the size of the ArrayList is 1 while the elementData length is 10(DEFAULT_CAPACITY).

If we add elements over the capacity, a new array will be created with larger capacity and the contents will be copied over.
- The original array will be left over for garbage collection.
As seen from the above code, every time the array list resizes, the capacity will grow by half of its current size. (newSize = currentSize * 1.5)
As this resizing process consumes resources, if you know approximately how many items will be stored in the ArrayList, it is better to specify the capacity when initializing the ArrayList.
- e.g) new ArrayList<>(CAPACITY)

Will the Guru