Are there any performance benefits if i call ArrayList.ensureCapacity() method. In what case it is advisable to make use of the method?
Are there any performance benefits if i call ArrayList.ensureCapacity() method. In what case it
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Are there any performance benefits if i call ArrayList.ensureCapacity() method. In what case it is advisable to make use of the method?
The performance benefit is realised in cases where you are about to add multiple elements to the list and know how many you’re going to be adding. By calling
ensureCapacity(int)you cause the underlying array to be resized once instead of potentially many times.Note however, that in reality you should rarely need to call this method; typically you will either instantiate the
ArrayListwith a known capacity, or in cases where the list size is unknown you should probably be considering using aLinkedListinstead.Also note that the resize strategy of
ArrayListis typically implemented in such a way that array copies are a rare operation (e.g. the capacity may increase by 50% every time the array becomes full). In other words, even if you do not callensureCapacityin advance you are unlikely to notice any slow-down within your code.