使用parallelStream代码

public static void main(String[] args) {        List
    
      ids1 = Lists.newArrayList();        List
     
       ids2 = Lists.newArrayList();        for(int i = 0; i < 1000; i ++){            ids1.add(i);        }        ids1.parallelStream().forEach(id ->ids2.add(id));    }
     
    

结果:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 823	at java.util.ArrayList.add(ArrayList.java:459)	at com.test.lambda$main$0(Md5Util.java:51)	at com.test$$Lambda$1/399573350.accept(Unknown Source)	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1374)	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:512)	at java.util.stream.ForEachOps$ForEachTask.compute(ForEachOps.java:290)	at java.util.concurrent.CountedCompleter.exec(CountedCompleter.java:731)	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:902)	at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1689)	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1644)	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)

因为parallelStream是并发流，当使用线程不安全的list的时候可能导致数组越界，可以使用线程安全的list，如下所示

List
    
      ids2 = Collections.synchronizedList(Lists.newArrayList());
    

如果使用 stream()方法，单线程处理也可以