First sorry for my poor english. I used proguard gui version 7.0 for obfuscating my jar made in jdk 14. I think that proguard occurs errors as a result to referenced jrt-fs.jar instead of rt.jar. From jdk9, there can't find rt.jar, so added jrt-fs.jar as reference library.
Anyone could help me to solve this problem?
Proguard error logs
Note: the configuration refers to the unknown class 'java.lang.String'
Note: the configuration refers to the unknown class 'java.lang.String'
Note: the configuration refers to the unknown class 'java.sql.Driver'
....
Proguard configuration
-injars 'C:\Users\common\SmartFoxServer_2X\SFS2X\extensions\Queen\QServerMainExtension.jar'
-outjars 'C:\Users\common\SmartFoxServer_2X\SFS2X\extensions\Queen\QServerMainExtension_small.jar'
-libraryjars 'C:\Program Files\Java\jdk-14.0.2\lib\jrt-fs.jar'
-libraryjars 'C:\Users\common\SmartFoxServer_2X\SFS2X\lib\sfs2x-core.jar'
-libraryjars 'C:\Users\common\SmartFoxServer_2X\SFS2X\lib\sfs2x.jar'
-libraryjars 'C:\Users\common\SmartFoxServer_2X\SFS2X\lib\slf4j-api-1.7.5.jar'
-libraryjars 'C:\Users\common\SmartFoxServer_2X\SFS2X\lib\slf4j-log4j12-1.7.5.jar'
...