Import the class having the getID() method.
We cannot guess which one it is... (there are perhaps a few dozen of classes with this method name, just in standard Java)
See also Lost file object from java api when updating and some other recent related threads.

Thanks PhiLho.

there are a few iava standard functions and methods used in my sketch, some of them were already identified.
for cannot find URLDecoder, just need to import java.net.*;
for cannot find Collections.sort, import java.util.*;

but for the function getID() is not exist, I still don't find which class should be imported.

Just now downgrade is a good choice.

done! thank you GoToLoop for your help:)

from the long list, I identified to import java.awt.event.MouseEvent is the key to let my skech re-work:

for the function getID() is not exist, import java.awt.event.MouseEvent;