一、什麼是ForkJoin
大數據裏面有map reduce ,Java從JDK1.7開始借鑑了這種分而治之的思想,提供ForkJoin框架用於並行執行任務,它的思想就是講一個大任務分割成若干小任務,最終彙總每個小任務的結果得到這個大任務的結果
Fork:把一個複雜任務進行分拆,大事化小
Join:把分拆任務的結果進行合併
二、3大類
2.1 ForkJoinPool
分支合併池 類比=> 線程池
2.2 ForkJoinTask
ForkJoinTask 類比=> FutureTask
2.3 RecursiveTask
遞歸任務:繼承後可以實現遞歸(自己調自己)調用的任務
三、使用示例
import java.util.concurrent.ExecutionException;
import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.ForkJoinTask;
import java.util.concurrent.RecursiveTask;
class MyTask extends RecursiveTask<Integer>{
private static final Integer ADJUST_VALUE = 10;
private int begin;
private int end;
private int result;
public MyTask(int begin, int end) {
this.begin = begin;
this.end = end;
}
@Override
protected Integer compute() {
if((end - begin)<=ADJUST_VALUE){
for(int i =begin;i <= end;i++){
result = result + i;
}
}else{
int middle = (begin + end)/2;
MyTask task01 = new MyTask(begin,middle);
MyTask task02 = new MyTask(middle+1,end);
task01.fork();
task02.fork();
result = task01.join() + task02.join();
}
return result;
}
}
/**
* 分支合併例子
* ForkJoinPool
* ForkJoinTask
* RecursiveTask
*/
public class ForkJoinDemo {
public static void main(String[] args) throws ExecutionException, InterruptedException {
MyTask myTask = new MyTask(0,100);
ForkJoinPool forkJoinPool = new ForkJoinPool();
ForkJoinTask<Integer> forkJoinTask = forkJoinPool.submit(myTask);
System.out.println(forkJoinTask.get());
forkJoinPool.shutdown();
}
}