type java -help in a command prompt and you should see -cp & -classpath to set the jars. these jars will be separate by ; in DOS and : in UNIX. If you are using Java 6+ you can just provide the folder names. Otherwise need to include individual jars.
c:\>java �cp c:/myProject com.xyz.client.Pet OR c:\>java -classpath c:/myProject/client.jar com.xyz.client.Pet