parallelStream是用的是默认线程池

整个应用会共用一个线程池，默认核心线程数为cpu核心数。

替换默认线程池

//自定义线程池
ForkJoinPool forkJoinPool = new ForkJoinPool(3);  
//提交的Runnable中运行parallelStream逻辑
forkJoinPool.submit(() -> {  
    firstRange.parallelStream().forEach((number) -> {
        try {
            Thread.sleep(5);
        } catch (InterruptedException e) { }
    });
});
 
ForkJoinPool forkJoinPool2 = new ForkJoinPool(3);  
forkJoinPool2.submit(() -> {  
    secondRange.parallelStream().forEach((number) -> {
        try {
            Thread.sleep(5);
        } catch (InterruptedException e) {
        }
    });
});