1. if the library is only folder not jar files, make it jar.
2. go to c:\program files\java\"version"\bin\
3. using cmd, enter java -jar cf "name_of_jar" "target_directory"
4. get jar file.
5. open android studio, add compile files('libs/your_lib')
6. rebuild project until it occur errors.
7. put lib to libs directory
8. rebuild project
9. OMG it works!