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As the picture shown, after one time run a method, i want remove the old items, and prepared for next time calculation, but i wondering how to remove elements in an arraylist start from an indicated index, like a queue, obey FIFO algorithm?
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ArrayList. remove(int index) method removes the element at the specified position in this list. Shifts any subsequent elements to the left (subtracts one from their indices).
We can use the remove() method of ArrayList container in Java to remove the first element. ArrayList provides two overloaded remove() method: remove(int index) : Accept index of the object to be removed. We can pass the first element's index to the remove() method to delete the first element.
You can use List#subList(int, int):
List<Integer> list = ...
list = list.subList(10, list.size()); // creates a new list from the old starting from the 10th element
or, since subList creates a view on which every modification affects the original list, this may be even better:
List<Integer> list = ...
list.subList(0, 10).clear(); // clears the first 10 elements of list
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