List的spliterator()是JDK1.8添加的方法，这个方法允许我们对一个集合对象中的元素进行分割，分割成多个小的集合对象，然后使用多线程并发处理，从而提升对集合的处理效率。
看demo：
/**
* ArrayList 并发迭代器使用方法
*/
public class TestArrayListIterator {
private static int LOOP_SIZE = 100;
public static void main(String[] args) throws Exception {
List<String> list = new ArrayList<>();
for(int i=0; i<LOOP_SIZE; i++) {
list.add(i+"-"+i);
}
Spliterator<String> spliterator = list.spliterator();
spliteratorList(spliterator);
Thread.sleep(10000);
}
public static void spliteratorList(Spliterator<String> splList) {
if(splList.estimateSize()>10) {
Spliterator<String> stringSpliterator = splList.trySplit();
spliteratorList(splList);
spliteratorList(stringSpliterator);
return;
}
new Thread(()->{
splList.forEachRemaining(x->System.out.println(Thread.currentThread().getName() + ":" + x));
}).start();
return;
}
}
/* 输出
Thread-0:93-93
Thread-12:18-18
Thread-12:19-19
Thread-12:20-20
Thread-12:21-21
Thread-12:22-22
Thread-12:23-23
Thread-12:24-24
Thread-11:25-25
Thread-11:26-26
Thread-10:31-31
Thread-10:32-32
Thread-10:33-33
Thread-10:34-34
Thread-10:35-35
Thread-10:36-36
Thread-15:0-0
Thread-15:1-1
Thread-15:2-2
Thread-15:3-3
Thread-15:4-4
Thread-15:5-5
Thread-6:56-56
Thread-6:57-57
Thread-6:58-58
Thread-6:59-59
Thread-6:60-60
Thread-6:61-61
Thread-9:37-37
Thread-9:38-38
Thread-9:39-39
Thread-9:40-40
Thread-9:41-41
Thread-9:42-42
Thread-13:12-12
Thread-13:13-13
Thread-13:14-14
Thread-13:15-15
Thread-13:16-16
Thread-13:17-17
Thread-3:75-75
Thread-3:76-76
Thread-3:77-77
Thread-3:78-78
Thread-2:81-81
Thread-2:82-82
Thread-2:83-83
Thread-2:84-84
Thread-2:85-85
Thread-2:86-86
Thread-4:68-68
Thread-4:69-69
Thread-4:70-70
Thread-4:71-71
Thread-4:72-72
Thread-4:73-73
Thread-4:74-74
Thread-7:50-50
Thread-7:51-51
Thread-7:52-52
Thread-7:53-53
Thread-7:54-54
Thread-7:55-55
Thread-5:62-62
Thread-1:87-87
Thread-1:88-88
Thread-5:63-63
Thread-5:64-64
Thread-5:65-65
Thread-5:66-66
Thread-5:67-67
Thread-3:79-79
Thread-3:80-80
Thread-11:27-27
Thread-11:28-28
Thread-11:29-29
Thread-11:30-30
Thread-0:94-94
Thread-0:95-95
Thread-0:96-96
Thread-0:97-97
Thread-0:98-98
Thread-0:99-99
Thread-14:6-6
Thread-14:7-7
Thread-14:8-8
Thread-14:9-9
Thread-14:10-10
Thread-14:11-11
Thread-8:43-43
Thread-8:44-44
Thread-8:45-45
Thread-8:46-46
Thread-8:47-47
Thread-8:48-48
Thread-8:49-49
Thread-1:89-89
Thread-1:90-90
Thread-1:91-91
Thread-1:92-92
*/这里的List中添加了100个元素，调用spliterator()方法进行分割，只要集合中的元素大于10个，就进行拆分。
分割是将集合一分为二，通过递归不停的调用自己，直到拆分的集合大小不大于10，则开始执行后续逻辑。