A Java KeyStore (JKS) is a repository of security certificates – either authorization certificates or public key certificates – plus corresponding private keys, used for instance in TLS encryption.
In IBM WebSphere Application Server and Oracle WebLogic Server, a file with extension jks serves as a keystore.
The Java Development Kit maintains a CA keystore file named cacerts in folder jre/lib/security.
JDKs provide a tool named keytool[1] to manipulate the keystore.
keytool has no functionality to extract the private key out of the keystore, but this is possible with third-party tools like jksExportKey, CERTivity,[2] Portecle[3] and KeyStore Explorer.