Modifying a jar file

Question

I have a jar file which is used in html file as applet. I want to modify the content of the jar file and to rebuild the jar file so that the html will work fine with the new jar file. How can i do this??

I already tried unzipping using 7zip nad modified the source and created the new jar. But when i use it in html it shows some java.lang.Classnotfound error

Answer 1

This is surely possible from the command line. Use the u option for jar

From the Java Tutorials:

jar uf jar-file input-file(s)

"Any files already in the archive having the same pathname as a file being added will be overwritten."

See Updating a JAR File

A brief test shows this quickly updates changes apart from trying to delete the file.

I haven't seen this answer on other threads about modifying jar files, and many, marked as duplicates, suggest there is no alternative but to remake the jar completely. Please correct if wrong.