线程和 BufferedReader

Question

当我想使用多线程作为键盘侦听器时遇到问题。

所以我写了这些代码。

private static boolean out=false;

public static  void main(String[] args)
{
    new Thread(new Runnable() {
        @Override
        public void run() {
            BufferedReader reader=new BufferedReader(new InputStreamReader(System.in));
            try{
                reader.readLine();
                reader.close();
            }catch (Exception e){e.printStackTrace();}
            out=true;
            System.out.println(" have received the keyboard");
        }
    }).start();

    new Thread(new Runnable() {
        @Override
        public void run() {

            while(true)
                if(out)
                    break;
            System.out.println(" exit the loop");
        }
    }).start();

}

但是当我在console输入东西的时候，第二个Thread好像不能运行.

如果我的代码或表达不清楚或有误，请告诉我。

谢谢！ `

Answer 1

一旦您执行程序，第二个线程就已经运行但由于您尚未为变量 out 分配新值 if -子句将始终并且无限计算为 false，因此永远不会中断。
您可以通过将 true 分配给 out 并使其成为 volatile 来解决此问题，以便始终使用最新更新的值。尝试这样的事情：

private static volatile boolean out = false;

  public static void main( String[] args )
  {
    new Thread( new Runnable()
    {
      @Override
      public void run()
      {
        BufferedReader reader = new BufferedReader( new InputStreamReader( System.in ) );
        try
        {
          reader.readLine();
          // will only be executed after input since BufferedReader.readLine() is blocking.
          out = true;
          reader.close();
        }
        catch ( Exception e )
        {
          e.printStackTrace();
        }
        System.out.println( " have received the keyboard" );
      }
    } ).start();

    new Thread( new Runnable()
    {
      @Override
      public void run()
      {
        // added to show that the 2nd thread started.
        System.out.println( "Thread 2 started running...." );

        while ( true )
          if ( out )
            break;
        System.out.println( " exit the loop" );
      }
    } ).start();
  }

线程和 BufferedReader

Thread and BufferedReader

java

io

multithreading

bufferedreader