class not found after compiling as Jar file

Question

There is a jar file already deployed and successfully running. And now we need to add a very small string in a class.

These are the steps so far i made:

1.) I already decompile/extract the jar into a folder. 
2.) Open a class file in JDgui(java file viewer).
3.) Copy the source code in notepad++ and save as fileName.java
4.) Compile that .java as .class via cmd.
5.) Compile the folder again as .jar file (the same as the old .jar which is running)

Now when i restarted Tomcat, run the system, then it showing the error:

ClassNotFoundException

When i open that jar file in JDGui the class is in it.

Please help. Thanks

Answer 1

This is no doubt coming from the error you naming the class differently or placing it in a different package (different folder).

When you save source of the class in a Java file, make sure you save it in a folder that reflects its package, and also place the package statement at the beginning of the file, reflecting the folder structure properly.

Also note that if the class is declared as public , it must be in a file named after the class: ClassName.java else it won't even compile. So you saving it in filename.java will not work in this case.

Also make sure you get no comile errors when you recompile this java file after modifying it (else you will not get a result .class file).