In this article, we will show the most efficient way finding or picking a element from List.
The basic idea for pick an item from list is, First generate a number which should be between 0 to list size.
1. Single Random Item
First we select a random index for using Random.nextInt(int bound) method. Instead of Random class, you can always use static method Math.random()(random() method generate an number between 0 to 1) and multiply it with list size.
2. Select Random Index In Multithread Environment
When we work with multithread applications using the single Random class instance then might result in picking same value for every process accessing this instance. Hence, We can always create a new instance per thread by using ThreadLocalRandom class.
3. Select Random Items With Repetitions List Element
Sometimes we want to pick few elements from a list. so first know how much element we want to select after that we select items one by one and add a new list and return it. Note: in this case one element may be select many times because we are not remove selected elements so list size remaining same.
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4. Select Random Items Without Repetitions List Element
Sometimes we want to pick few elements from a list. so first make sure how much element we want to select after that we select items one by one and add a new list and return it. Note: in this case one element select only ones because we are remove selected elements, so decrease list size also automatic by JVM.
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