Java并发编程：Fork/Join框架机制详解

cicadasmile · cicadasmile · commit ccd63f8d128f · 2020-08-16T15:42:24.000+08:00
diff --git a/java-se-base-parent/model-multy-thread/src/main/java/com/multy/thread/block07forkjoin/ForkJoin01.java b/java-se-base-parent/model-multy-thread/src/main/java/com/multy/thread/block07forkjoin/ForkJoin01.java
@@ -0,0 +1,65 @@
+package com.multy.thread.block07forkjoin;
+
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.ForkJoinTask;
+import java.util.concurrent.RecursiveTask;
+
+public class ForkJoin01 {
+
+    public static void main (String[] args) {
+        int[] numArr = new int[100];
+        for (int i = 0; i < 100; i++) {
+            numArr[i] = i + 1;
+        }
+        ForkJoinPool pool = new ForkJoinPool();
+        ForkJoinTask<Integer> forkJoinTask =
+                pool.submit(new SumTask(numArr, 0, numArr.length));
+        System.out.println("合并计算结果: " + forkJoinTask.invoke());
+        pool.shutdown();
+    }
+}
+/**
+ * 线程任务
+ */
+class SumTask extends RecursiveTask<Integer> {
+    /*
+     * 切分任务块的阈值
+     * 如果THRESHOLD=100
+     * 输出：main【求和：(0...100)=5050】 合并计算结果: 5050
+     */
+    private static final int THRESHOLD = 100;
+    private int arr[];
+    private int start;
+    private int over;
+
+    public SumTask(int[] arr, int start, int over) {
+        this.arr = arr;
+        this.start = start;
+        this.over = over;
+    }
+
+    // 求和计算
+    private Integer sumCalculate () {
+        Integer sum = 0;
+        for (int i = start; i < over; i++) {
+            sum += arr[i];
+        }
+        String task = "【求和：(" + start + "..." + over + ")=" + sum +"】";
+        System.out.println(Thread.currentThread().getName() + task);
+        return sum ;
+    }
+
+    @Override
+    protected Integer compute() {
+        if ((over - start) <= THRESHOLD) {
+            return sumCalculate();
+        }else {
+            int middle = (start + over) / 2;
+            SumTask left = new SumTask(arr, start, middle);
+            SumTask right = new SumTask(arr, middle, over);
+            left.fork();
+            right.fork();
+            return left.join() + right.join();
+        }
+    }
+}
