Java线程池示例：并行计算200000以内的质数个数

野性酷女 2023-10-08 09:27 46阅读 0赞

static void countTime() throws Exception {
            long start = System.currentTimeMillis();
            List<Integer> list = getPrime(1, 200000);
            long end  = System.currentTimeMillis();
            System.out.println("普通计算耗时："+(end-start));
            System.out.println("=================================");
            final int cpuCoreNum = 4;
            ExecutorService service = Executors.newFixedThreadPool(cpuCoreNum);
    
            MyTask task1 = new MyTask(1, 80000);
            MyTask task2 = new MyTask(80001, 130000);
            MyTask task3 = new MyTask(130001, 170000);
            MyTask task4 = new MyTask(170001, 200000);
            Future<List<Integer>> f1 = service.submit(task1);
            Future<List<Integer>> f2 = service.submit(task2);
            Future<List<Integer>> f3 = service.submit(task3);
            Future<List<Integer>> f4 = service.submit(task4);
            long s = System.currentTimeMillis();
            List<Integer> list1 = f1.get();
            List<Integer> list2 = f2.get();
            List<Integer> list3 = f3.get();
            List<Integer> list4 = f4.get();
            long e = System.currentTimeMillis();
            System.out.println("并行计算耗时："+(e-s));
        }
    
        static class MyTask implements Callable<List<Integer>>{
            int startPos,endPos;
    
            public MyTask(int startPos, int endPos) {
                this.startPos = startPos;
                this.endPos = endPos;
            }
    
            @Override
            public List<Integer> call() throws Exception {
                List<Integer> list = getPrime(startPos, endPos);
                return list;
            }
        }
    
        //判断一个数是不是质数
        static boolean isPrime(int num){
            for (int i = 2; i < num/2; i++) {
                if (num%i==0) return false;
            }
            return true;
        }
    
        static List<Integer> getPrime(int start,int end){
            List<Integer> results = new ArrayList<>();
            for (int i = start; i < end; i++) {
                if (isPrime(i)) results.add(i);
            }
            return results;
        }

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[20191109114808883.png]: https://img-blog.csdnimg.cn/20191109114808883.png