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Fork/Join分支合并框架
在必要的情况下,将一个大任务拆分成多个小任务(不可再拆分),然后将小任务的计算结果进行汇总。
工作窃取模式
当一个线程上获取不到任务的时候,它将会到其他线程的尾部去截取一个任务来执行。
public class ThreadTest {
public static void main(String[] args) {
ForkJoinPool pool = new ForkJoinPool();
ForkJoinTask<Long> task = new ForkJoinDemo(0L, 100000000L);
Long sum = pool.invoke(task);
System.out.println(sum);
}
}
class ForkJoinDemo extends RecursiveTask<Long>{
private static final long serivalVersionUID = -5235345621564052455L;
private long start;
private long end;
private static final long THURSHOLD = 10000L;//临界值
public ForkJoinDemo(long start,long end) {
this.start = start;
this.end = end;
}
@Override
protected Long compute() {
long length = end - start;
if(length<=THURSHOLD){
long sum = 0L;
for (long i=start;i< end;i++){
sum+=i;
}
return sum;
}else{
long middle = (start + end)/2;
ForkJoinDemo left = new ForkJoinDemo(start,middle);
left.fork();//进行拆分,压入队列
ForkJoinDemo right = new ForkJoinDemo(middle+1,end);
right.fork();
return left.join() + right.join();
}
}
}