You need to copy sapjco3.dll in a folder in your Java library path as he t library is not sapjco3.jar and it is a sapjco3.dll file.
You can call in your application usingfollowing:
Following approaches can be used:
First is by copying sapjco3.dll into one of the folder which are already in your library path like: C:\WINNT\system32
Second would be to use the same path in Java library path using any of the following options:
By accessing System.setProperty ("java.library.path","C:\path\to\folder\with\dll\") before accessing the SAPJCo
You can set Java command line like this -Djava.library.path=C:\path\to\folder\with\dll\