from java.net import URL
from java.util.jar import JarInputStream
jar_location = "file:///usr/share/java/libgcj-4.4.jar"
inStream = JarInputStream(URL(jar_location).openStream(), True)
# print an entry with max size
entry = max(iter(inStream.getNextJarEntry, None), key=lambda entry: entry.size)
print entry.name, entry.size
выход
gnu/javax/net/ssl/StaticTrustAnchors.class 92341