Java class files are often distributed as jar files, which are collections of individually compressed class files (and possibility other files). Jar files are typically about 1/2 the size of the original class files due to compression. I have developed a wire-code format for collections of Java class files. This format is typically 1/2 to 1/5 of the size of the corresponding compressed jar file (1/4 to 1/10 the size of the original class files).