The default constructor for this class creates invalid object:

       This should not compile.

_______________________Example ______________________________________
import java.io.*;

public class bug_test {
  public static void main( String argv[] ) {

 FileDescriptor fdesc=new FileDescriptor(); // We create not valid object
     
 if ((fdesc!=null) && (fdesc instanceof FileDescriptor)) // Verify all
   
  if ( ! fdesc.valid() ) // Not represents an active connection
  {
   System.out.println("Not valid !");
   return;
  }

    System.out.println("Valid ??");
  }
}
____ This test successfully compiles and produces output: ______

Not valid !