Java内容重新整理删除过期的东西

Java/JavaDemo/codedemo/java/util/forkjoin/HelloForkJoin.java

@@ -0,0 +1,103 @@
+package cn.aofeng.demo.java.util.forkjoin;
+
+import java.util.Arrays;
+import java.util.concurrent.ForkJoinPool;
+import java.util.concurrent.RecursiveTask;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Fork/Join练习。
+ * 
+ * @author <a href="mailto:aofengblog@163.com">聂勇</a>
+ */
+public class HelloForkJoin extends RecursiveTask<Long> {
+
+    private static final long serialVersionUID = -2386438994963147457L;
+
+    private int[] _intArray;
+    
+    private int _threshold = 10;
+    
+    private long _result = 0;
+    
+    public HelloForkJoin(int[] intArray) {
+        this._intArray = intArray;
+    }
+    
+    @Override
+    protected Long compute() {
+        if (null == _intArray || _intArray.length <= 0) {
+            return 0L;
+        }
+        
+        if (_intArray.length <= _threshold) {   // 如果数组长度小于等于指定的值，执行累加操作
+            for (int item : _intArray) {
+                _result += item;
+            }
+            System.out.println( String.format("线程：%s，累加数组%s中的值，结果：%d", Thread.currentThread(), Arrays.toString(_intArray), _result) );
+        } else {   // 如果数组长度大于指定的值，做任务分解
+            int[] temp = new int[_threshold];
+            System.arraycopy(_intArray, 0, temp, 0, _threshold);
+            HelloForkJoin subTask1 = new HelloForkJoin(temp);
+            subTask1.fork();
+            
+            if (_intArray.length - _threshold > 0) {
+                int remain[] = new int[_intArray.length - _threshold];
+                System.arraycopy(_intArray, _threshold, remain, 0, remain.length);
+                HelloForkJoin task = new HelloForkJoin(remain);
+                task.fork();
+                _result += task.join();
+            }
+            
+            _result += subTask1.join();
+            
+            return _result;
+        }
+        
+        return _result;
+    }
+    
+    public static void main(String[] args) throws InterruptedException {
+        int count = 10000;
+        
+        serialCompute(count);
+        parallelCompute(count);
+    }
+
+    /**
+     * 使用fork/join并行计算数字累加。
+     * 
+     * @param count 数字个数（从1开始）
+     * @throws InterruptedException
+     */
+    private static void parallelCompute(int count)
+            throws InterruptedException {
+        int[] numbers = new int[count];
+        for (int i = 0; i < count; i++) {
+            numbers[i] = i+1;
+        }
+        ForkJoinPool pool = new ForkJoinPool(4);
+        HelloForkJoin task = new HelloForkJoin(numbers);
+        long startTime = System.currentTimeMillis();
+        pool.submit(task);
+        pool.shutdown();
+        pool.awaitTermination(10, TimeUnit.SECONDS);
+        
+        System.out.println( String.format("并行计算结果：%d，耗时：%d毫秒", task._result, System.currentTimeMillis()-startTime) );
+    }
+
+    /**
+     * 使用for循环串行计算数字累加。
+     * 
+     * @param count 数字个数（从1开始） 
+     */
+    private static void serialCompute(int count) {
+        long startTime = System.currentTimeMillis();
+        int sum = 0;
+        for (int i = 0; i < count; i++) {
+            sum += (i+1);
+        }
+        System.out.println( String.format("串行计算结果：%d，耗时：%d毫秒", sum, System.currentTimeMillis()-startTime) );
+    }
+
+}