How do I list and export a private key from a keystore?
Another great tool is KeyStore Explorer: http://keystore-explorer.sourceforge.net/
If you don't need to do it programatically, but just want to manage your keys, then I've used IBM's free KeyMan tool for a long time now. Very nice for exporting a private key to a PFX file (then you can easily use OpenSSL to manipulate it, extract it, change pwds, etc).
https://www.ibm.com/developerworks/mydeveloperworks/groups/service/html/communityview?communityUuid=6fb00498-f6ea-4f65-bf0c-adc5bd0c5fcc
Select your keystore, select the private key entry, then File->Save to a pkcs12 file (*.pfx, typically). You can then view the contents with:
$ openssl pkcs12 -in mykeyfile.pfx -info
Another less-conventional but arguably easier way of doing this is with JXplorer. Although this tool is designed to browse LDAP directories, it has an easy-to-use GUI for manipulating keystores. One such function on the GUI can export private keys from a JKS keystore.