使用InStream的多线程方法向synchronizedList中插入若干个随机数，并计算其中重复的个数。

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List<Integer> numberList = Collections.synchronizedList(new ArrayList<>());
//
IntStream.range(0, 100).parallel().forEach(i -> {
    numberList.add(new Random().nextInt(100));
});
List<Integer> filterNumberList = numberList.stream().distinct().collect(Collectors.toList());

System.out.println("numberList.size = " + numberList.size());
System.out.println("filterNumberList.size = " + filterNumberList.size());
System.out.println("重复个数：" + (numberList.size() - filterNumberList.size()));