libbcel-java 6.3-1 (amd64 binary) in ubuntu focal

 The Byte Code Engineering Library is intended to give users a convenient
 possibility to analyze, create, and manipulate (binary) Java class files
 (those ending with .class). Classes are represented by objects which contain
 all the symbolic information of the given class: methods, fields and byte
 code instructions, in particular.
 .
 Such objects can be read from an existing file, be transformed by a program
 (e.g. a class loader at run-time) and dumped to a file again. An even more
 interesting application is the creation of classes from scratch at run-time.
 The Byte Code Engineering Library (BCEL) may be also useful if you want to
 learn about the Java Virtual Machine (JVM) and the format of Java .class
 files.