java jdb如何打印变量属于父类

Question

我正在调试jdk中的类sun/net/www/protocol/jar/JarURLConnection$JarURLInputStream，这是JarURLConnection的内部类

JarURLInputStream extends FilterInputStream
  {
    JarURLInputStream(InputStream paramInputStream)
    {
      super();
    }

    public void close()
      throws IOException
    {
      try
      {
        super.close();
      }
      finally
      {
        if (!JarURLConnection.this.getUseCaches()) {
          JarURLConnection.this.jarFile.close();
        }
      }
    }
  }

我这样设置断点：

stop in sun.net.www.protocol.jar.JarURLConnection$JarURLInputStream.close

击中断点时，我想知道

的值

JarURLConnection.this.jarFile.getName()

像这样：

print JarURLConnection.this.jarFile.getName()
com.sun.tools.example.debug.expr.ParseException: Name unknown: JarURLConnection
 JarURLConnection.this.jarFile.getName() = 空值

但是它不起作用，正确的方法是什么？