如何在 Java 中的特定时间后中断方法？

Question

我需要编写一个简单的程序来打印不超过给定数字但不超过 5 秒的素数。一段时间后是否有某种计时器可用于中断方法？（但如果打印时间短于 5 秒则不会中断）。提前致谢。

我的代码：

public class Primes {
    private static boolean checkIfPrime(int x) {
        if (x == 2) return true;
        if (x % 2 == 0) return false;
        int sqrt = (int) Math.sqrt(x) + 1;
        for (int i = 3; i < sqrt; i = i + 2) if (x % i == 0) return false;
        return true;
    }

    private static void printPrimesAndOperationTime(int n) {
        long start = System.nanoTime();
        for (int i = 2; i <= n; i++) if (checkIfPrime(i)) System.out.println(i);
        long end = System.nanoTime();

        long timeResult = end - start;
        System.out.println("Printing time = " + timeResult + " [ns] => "
                + Math.round(timeResult * 100.0 / 1000000) / 100.0 + " [ms]");
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();

        printPrimesAndOperationTime(n);
    }
}

Answer 1

使用Java并发API解决了上述问题。请查找代码遍历的内联注释。

import java.util.Scanner;
import java.util.concurrent.*;

public class TimeoutInterval {
    public static void main(String[] args) throws Exception {
        ExecutorService executor = Executors.newSingleThreadExecutor(); // Start Single thread executor
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        Future future = executor.submit(new Primes(n)); // Find prime no.
        try {
            future.get(5, TimeUnit.SECONDS); // Set the time out of the prime no. search task
            executor.shutdown();
        } catch (TimeoutException e) {
            executor.shutdown();
            System.out.println("Terminated!");
        }

        executor.shutdownNow();
    }
}

class Primes  implements Runnable {
    private final int number;

    Primes(int number) {
        this.number = number;
    }
    @Override
    public void run() {
        System.out.println("Started..");
        printPrimesAndOperationTime(number);
        System.out.println("Finished!");
    }

    private static boolean checkIfPrime(int x) {
        if (x == 2) return true;
        if (x % 2 == 0) return false;
        int sqrt = (int) Math.sqrt(x) + 1;
        for (int i = 3; i < sqrt; i = i + 2) if (x % i == 0) return false;
        return true;
    }

    private static void printPrimesAndOperationTime(int n) {
        long start = System.nanoTime();
        for (int i = 2; i <= n && !Thread.interrupted(); i++) if (checkIfPrime(i)) {
            System.out.println(i);
        }
        long end = System.nanoTime();

        long timeResult = end - start;
        System.out.println("Printing time = " + timeResult + " [ns] => "
                + Math.round(timeResult * 100.0 / 1000000) / 100.0 + " [ms]");
    }

}

Answer 2

使用ExecutorService，您可以提交一个超时的任务。在收到 TimeoutException 时，您应该在任务上调用 cancel(true) 方法来中断线程。

来自documentation

... If the task has already started, then the mayInterruptIfRunning parameter determines whether the thread executing this task should be interrupted in an attempt to stop the task.

如何在 Java 中的特定时间后中断方法？

How to interrupt a method after specific time in Java?

java

interruption