有时并发代码确实可能比顺序代码慢，这可能是由于后者的内存访问模式更好。解决方法是优化并发代码以最大程度地利用多个处理器核心。例如，使用锁来避免竞争条件，使用线程池来避免线程创建和销毁的成本，并使用异步编程API来减少阻塞和等待时间。以下是一个范例代码：

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ConcurrentVsSequential {

    public static void main(String[] args) {
        long startTime = System.currentTimeMillis();
        sequentialTask();
        long endTime = System.currentTimeMillis();
        System.out.println("Sequential Time Taken: " + (endTime - startTime) + "ms");

        startTime = System.currentTimeMillis();
        concurrentTask();
        endTime = System.currentTimeMillis();
        System.out.println("Concurrent Time Taken: " + (endTime - startTime) + "ms");
    }

    private static void sequentialTask() {
        for (int i = 0; i < 10_000_000; i++) {
            Math.sqrt(i);
        }
    }

    private static void concurrentTask() {
        ExecutorService executorService = Executors.newFixedThreadPool(10);
        for (int i = 0; i < 10_000_000; i++) {
            executorService.execute(() -> Math.sqrt(i));
        }
        executorService.shutdown();
    }
}