The first step is to determine the metacode compilation version. The minor version is not important, at least the major version should be correct.
The second step is to build a project in eclipse, making the compilation environment and meta-environment the same, and taking this jar package and the jar package that the jar package depends on as the dependency library.
The third step is to create packages and java files (as long as you modify them) according to the requirements of class, paste the decompiled code and then modify it.
The fourth step, as long as the compilation passes, enter the classes directory and copy that class file into the jar package.
However, it should be noted that all constants of 1 will display their values directly in the decompiled class and will not point to the constant file (it doesn't matter, just change it directly).
The number of rows does not match the source code. Source code comments take up a few lines, and decompilation has no comments.
3 Some codes cannot be decompiled. Like confusion, or a higher version.