ForkJoinPool使用示例：进行数组数据的并行计算

川长思鸟来 2023-10-05 09:46 9阅读 0赞

package com.zhangxueliang.juc;
    
    import java.io.IOException;
    import java.util.Arrays;
    import java.util.Random;
    import java.util.concurrent.ForkJoinPool;
    import java.util.concurrent.RecursiveAction;
    import java.util.concurrent.RecursiveTask;
    
    public class ForkJoinPoolDemo {
        
    	static int[] nums = new int[1000000];
    	static final int MAX_NUM = 50000;
    	static Random r = new Random();
    	
    	static {
        
    		for(int i=0; i<nums.length; i++) {
        
    			nums[i] = r.nextInt(100);
    		}
    		
    		System.out.println("---" + Arrays.stream(nums).sum()); //stream api
    	}
    	
    
    	static class AddTask extends RecursiveAction {
        
    
    		int start, end;
    
    		AddTask(int s, int e) {
        
    			start = s;
    			end = e;
    		}
    
    		@Override
    		protected void compute() {
        
    
    			if(end-start <= MAX_NUM) {
        
    				long sum = 0L;
    				for(int i=start; i<end; i++) sum += nums[i];
    				System.out.println("from:" + start + " to:" + end + " = " + sum);
    			} else {
        
    
    				int middle = start + (end-start)/2;
    
    				AddTask subTask1 = new AddTask(start, middle);
    				AddTask subTask2 = new AddTask(middle, end);
    				subTask1.fork();
    				subTask2.fork();
    			}
    
    
    		}
    
    	}
    
    	
    	static class AddTaskRet extends RecursiveTask<Long> {
        
    		
    		private static final long serialVersionUID = 1L;
    		int start, end;
    		
    		AddTaskRet(int s, int e) {
        
    			start = s;
    			end = e;
    		}
    
    		@Override
    		protected Long compute() {
        
    			
    			if(end-start <= MAX_NUM) {
        
    				long sum = 0L;
    				for(int i=start; i<end; i++) sum += nums[i];
    				return sum;
    			} 
    			
    			int middle = start + (end-start)/2;
    			
    			AddTaskRet subTask1 = new AddTaskRet(start, middle);
    			AddTaskRet subTask2 = new AddTaskRet(middle, end);
    			subTask1.fork();
    			subTask2.fork();
    			
    			return subTask1.join() + subTask2.join();
    		}
    		
    	}
    	
    	public static void main(String[] args) throws IOException {
        
    		/*ForkJoinPool fjp = new ForkJoinPool();
    		AddTask task = new AddTask(0, nums.length);
    		fjp.execute(task);*/
    
    		ForkJoinPoolDemo temp = new ForkJoinPoolDemo();
    
    		ForkJoinPool fjp = new ForkJoinPool();
    		AddTaskRet task = new AddTaskRet(0, nums.length);
    		fjp.execute(task);
    		long result = task.join();
    		System.out.println(result);
    		
    		//System.in.read();
    		
    	}
    }