Question

我编写了一个生成1到1,000之间随机数的程序。然后，它使用三个线程的线程池来搜索范围更广的1到1,000范围内的某些数字范围。线程检查其范围内的每个数字，并将其与随机目标数量进行比较，如果匹配，则向控制台发送的消息会这样说。如果数字不匹配，这也会反映在控制台的消息中。我试图弄清楚如何在达到目标数量后结束程序，并且即使已找到目标，也不会继续分析数字。谢谢。

这是FindIt类：

/** fill in later */
public class FindIt extends Thread
{
    private int numToFind;
    private int numToStart;
    private int numToEnd;

    public FindIt( int nF, int nS, int nE )
    {
        numToFind = nF;
        numToStart = nS;
        numToEnd = nE;
    }

    public void run()
    {
        int counter = 0;

        int numAt = numToStart;

        for ( int i = 0; i < ( numToEnd - numToStart ) + 1; i++ )
        {
            counter++;

            if ( counter == 10 )
            {
                counter = 0;
                Thread.yield();
            }

            if ( numAt++ == numToFind )
            {
                System.out.println( "The target number, " + numToFind + ", has been found by " + Thread.currentThread().getName() + "." );
            }

            else
            {
                System.out.println( Thread.currentThread().getName() + " has analyzed the number " + ( numAt - 1 ) + " - not the target number." );
            }

        }   
    }
}

这是主程序的程序：

import java.util.Random; //imports Java's Random class
import java.util.concurrent.*;

/** fill in later */
public class NumberSearch
{
    public static void main( String [] args )
    {
        Random r = new Random(); //creates an instance of the Random class
        int randomNum = r.nextInt( 1001 ); //declares the integer randomNum and initilizes it to be a random interger in the range 0 inclusive to 1001 exclusive

        ExecutorService executor = Executors.newFixedThreadPool( 3 );

        FindIt find1 = new FindIt( randomNum, 0, 349);
        FindIt find2 = new FindIt( randomNum, 350, 699);
        FindIt find3 = new FindIt( randomNum, 700, 1000);

        executor.execute( find1 );
        executor.execute( find2 );
        executor.execute( find3 );

        executor.shutdown();
    }
}

Answer 1

需要做两件事：

通过检查Thread.currentThread().isInterrupted()并在检测到中断时让任务返回来使您的任务对中断做出响应。
使用ExecutorService的shutdownNow方法来中断当前正在运行的任务。 shutdown方法使执行程序停止接收新任务，但允许已提交给执行程序的任务运行完毕。

不要为此子类化Thread，您应该扩展Runnable或Callable以定义提交给Executor的任务。子类化线程意味着任务分配OS线程，这是不必要的，因为已经在线程池中创建了实际线程。对于此示例，由于您正在计算任务中的数字，因此使用Callable可能是有意义的。

java.util.concurrent中存在一个专为此类设计的类。一旦找到答案，取消任务的示例在API documentation for ExecutorCompletionService。

中给出

FindIt已更改为检测中断：

public class FindIt implements Runnable
{
    private int numToFind;
    private int numToStart;
    private int numToEnd;

    public FindIt( int nF, int nS, int nE )
    {
        numToFind = nF;
        numToStart = nS;
        numToEnd = nE;
    }

    public void run()
    {
        int counter = 0;

        int numAt = numToStart;

        for ( int i = 0; i < ( numToEnd - numToStart ) + 1; i++ )
        {
            if (Thread.currentThread().isInterrupted()) {
                System.out.println(Thread.currentThread().getName() 
                + " detected interruption, exiting");
                return;
            }
            counter++;

            if ( counter == 10 )
            {
                counter = 0;
                Thread.yield();
            }

            if ( numAt++ == numToFind )
            {
                System.out.println( "The target number, " + numToFind + ", has been found by " + Thread.currentThread().getName() + "." );
            }

            else
            {
                System.out.println( Thread.currentThread().getName() + " has analyzed the number " + ( numAt - 1 ) + " - not the target number." );
            }

        }   
    }
}

如何在Java

1 个答案: