I'm running ProGuard to shrink my jar file. One of the parameters it needs is the system's runtime jar. This is at $JAVA_HOME/lib/rt.jar on Sun distributions, but not on Apple's Mac OS X (v10.6 (Snow Leopard) in my case).
Is there an rt.jar for OS X?
It is called classes.jar and it is under /System/Library/Frameworks/JavaVM.framework/Classes
Look here for details:
http://lists.apple.com/archives/java-dev/2003/Mar/msg01530.html
This blog entry describes a relatively straight-forward way to resolve the issue without modifying the Proguard configuration.
The entry recommends that two symbolic links are created, so that rt.jar and jsse.jar exist in the path that Proguard expects them to.
Standing in the /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/lib directory and running the following commands resolved the problem for me:
sudo ln -s ../../Classes/classes.jar rt.jar
sudo ln -s ../../Classes/jsse.jar .
There's some explanation of how to get to the rt.jar equivalent in the What should I set JAVA_HOME to on OSX question.
The short answer is to use the result of /usr/libexec/java_home or to set JAVA_HOME to $(/usr/libexec/java_home) and then find classes.jar (the OS X equivalent of rt.jar) at JAVA_HOME/bundle/Classes/classes.jar
On my system (Mojave 10.14.3 with JDK1.8), there is no classes.jar except in gradle caches (~/.gradle/caches/). There is, however, an rt.jar in /Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/jre/lib/rt.jar. I linked it and jsse.jar in the same way as Henrik from the Contents/Home/lib folder:
➜ lib sudo ln -s ../jre/lib/rt.jar
➜ lib sudo ln -s ../jre/lib/jsse.jar
and Proguard works now.
来源：https://stackoverflow.com/questions/2776359/running-proguard-on-os-x-where-is-apples-equivalent-to-the-rt-jar