使用jnativeHook记录击键时无法看到输出

Question

我正在尝试记录击键，当我执行一些关键事件，如左，右，移动，按下，释放等。最初，当我编写代码并编译它时，我能够记录击键。但是，当我在一点代码缩进后编译时，它显示以下语句

  Process finished with exit code 0

发布的是我的代码：

public class key_logger implements NativeKeyListener {

public void nativeKeyPressed(NativeKeyEvent e) {

    System.out.println("Key Pressed: " + NativeKeyEvent.getKeyText(e.getKeyCode()));

          if (e.getKeyCode() == NativeKeyEvent.VK_ESCAPE)
          {

               GlobalScreen.unregisterNativeHook();
           }

  }

public void nativeKeyReleased(NativeKeyEvent e) {

    System.out.println("Key Released: " + NativeKeyEvent.getKeyText(e.getKeyCode()));

}

public void nativeKeyTyped(NativeKeyEvent e) {

    System.out.println("Key Typed: " + e.getKeyText(e.getKeyCode()));

}

public static void main(String[] args) {

    try {

        GlobalScreen.registerNativeHook();

    }

    catch (NativeHookException ex) {

        System.err.println("There was a problem registering the native hook.");

        System.err.println(ex.getMessage());

        System.exit(1);
    }

    //Construct the example object and initialze native hook.
    GlobalScreen.getInstance().addNativeKeyListener(new key_logger());
}
  }