If you want to develop Java programs yourself, you install the JDK. The JDK, on the other hand, packages the JRE along with all the necessary libraries for developing Java programs. If you would like to understand the architecture of JVM at a deeper level, I would suggest Siben Nayak's in-depth article on the topic. [...]

The returned CertPath object does not include the most-trusted CA certificate that may have been used to anchor the path. Instead, use the getTrustAnchor method to get the Certificate of the most-trusted CA. An X.509 CertPath object and a PKIXParameters object are passed as arguments to the validate https://remotemode.net/ method of a CertPathValidator instance implementing [...]