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import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.Future;
import java.util.concurrent.RecursiveTask;
import java.util.concurrent.atomic.AtomicIntegerArray;
public class CountTask extends RecursiveTask<Integer> {
private static final int THRESHOLD = 2; // 阈值
private int start;
private int end;
public CountTask(int start, int end) {
this.start = start;
this.end = end;
}
public int getStart() {
return start;
}
public int getEnd() {
return end;
}
@Override
protected Integer compute() {
int sum = 0;
// 如果任务足够小就计算任务
boolean canCompute = (end - start) <= THRESHOLD;
if (canCompute) {
for (int i = start; i <= end; i++) {
sum += i;
}
} else {
// 如果任务大于阈值,就分裂成两个子任务计算
int middle = (start + end) / 2;
CountTask leftTask = new CountTask(start, middle);
CountTask rightTask = new CountTask(middle + 1, end);
System.out.println("leftTask:" + leftTask.getStart() + "," + leftTask.getEnd());
System.out.println("rightTask:" + rightTask.getStart() + "," + rightTask.getEnd());
// 执行子任务
leftTask.fork();//每个子任务在调用fork方法时,又会进入compute方法
rightTask.fork();
// 等待子任务执行完,并得到其结果
int leftResult = leftTask.join();
int rightResult = rightTask.join();
System.out.println(leftResult + "," + rightResult);
// 合并子任务
sum = leftResult + rightResult;
}
return sum;
}
public static void main(String[] args) {
ForkJoinPool forkJoinPool = new ForkJoinPool();
// 生成一个计算任务,负责计算1+2+3+4
CountTask task = new CountTask(1, 10);
// 执行一个任务
Future<Integer> result = forkJoinPool.submit(task);
try {
System.out.println(result.get());
} catch (InterruptedException e) {
} catch (ExecutionException e) {
}
//------------------------
int[] value = new int[]{1, 2};
AtomicIntegerArray ai = new AtomicIntegerArray(value);
System.out.println(ai.getAndSet(0, 3));//返回原来的值
System.out.println(ai.get(0));
System.out.println(value[0]);
}
}
输出:
leftTask:1,5
rightTask:6,10
leftTask:1,3
rightTask:4,5
6,9
leftTask:6,8
rightTask:9,10
21,19
15,40
55