HashSet to array

Development process , We often put data into sets for operation , because java Collections provide us with a large number of methods and functions to use , It greatly reduces our development workload . But sometimes what we need is the basic data type , For example, array , At this point, we convert the collection type into an array . Although the collection class has a toArray() Method , But back Object[] type , Usually we can consider using stream Flow forward , The reference codes are as follows ：

HashSet<Integer> set = new HashSet();
int[] a = set.stream().mapToInt(Integer::intValue).toArray()