多线程判断素数Java代码

以下是判断素数的 Java 代码，可以使用多线程进行优化：

import java.util.concurrent.*;

public class PrimeNumberChecker {
    public static boolean isPrime(int n) {
        if (n <= 1) {
            return false;
        }

        for (int i = 2; i <= Math.sqrt(n); i++) {
            if (n % i == 0) {
                return false;
            }
        }

        return true;
    }

    public static void main(String[] args) throws Exception {
        int[] numbers = { 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 };
        int threads = Runtime.getRuntime().availableProcessors();
        ExecutorService service = Executors.newFixedThreadPool(threads);

        for (int i = 0; i < numbers.length; i++) {
            int n = numbers[i];

            service.submit(() -> {
                if (isPrime(n)) {
                    System.out.println(n + " is prime");
                } else {
                    System.out.println(n + " is not prime");
                }
            });
        }

        service.shutdown();
        service.awaitTermination(1, TimeUnit.MINUTES);
    }
}

这段代码使用了线程池来并发执行素数判断任务，提高了程序的效率。