how can open JAR file and editing some thing inside file class and create JAR file again ?

1) Make changes to your java file and compile it to convert it into a class file.
2) Open a jar file using winzip or 7-zip.
3) Drag and drop your changed class in this opened JAR file to its proper location.This step will replace the old class file.
4) Save the Changes.

Please note this can be done for development environment and not recommended for production/UAT environment.

Cheers,
Sudhakar