I tried with this command:
keytool -keypasswd -keystore mykeystore.jks -alias key0
and I get this:
keytool error: java.lang.UnsupportedOperationException: -keypasswd commands not supported if -storetype is PKCS12
however the output of:
keytool -list -keystore mykeystore.jks -v
is the following:
Enter keystore password:
Keystore type: JKS
Keystore provider: SUN
Your keystore contains 1 entry
Alias name: key0
Creation date: 21 Dec 2017
Entry type: PrivateKeyEntry
Certificate chain length: 1
Certificate[1]:
...