add ParallelStreamDemo

src/test/java/com/alibaba/demo/forkjoinpool/Demo.kt

@@ -25,7 +25,7 @@ internal class SumTask(private val numbers: LongRange) : RecursiveTask<Long>() {
     override fun compute(): Long =
             if (numbers.count() <= 16) {
                 // compute directly
-                numbers.asSequence().sum()
+                numbers.sum()
             } else {
                 // split task
                 val middle = numbers.start + numbers.count() / 2

src/test/java/com/alibaba/demo/forkjoinpool/ParallelStreamDemo.kt

+package com.alibaba.demo.forkjoinpool
+
+import java.util.concurrent.ConcurrentSkipListSet
+
+fun main(args: Array<String>) {
+    println("availableProcessors: ${Runtime.getRuntime().availableProcessors()}")
+
+    val threadNames: MutableSet<String> = ConcurrentSkipListSet()
+
+    (0..100).toList().stream().parallel().mapToInt {
+        threadNames.add(Thread.currentThread().name)
+        Thread.sleep(10)
+        println("${Thread.currentThread().name}: $it")
+        it
+    }.sum().let {
+        println(it)
+    }
+
+    println("${threadNames.size}:\n$threadNames")
+}