IntelliJ says the package does not exist, But I can access the package
I had similar issue with different package:
package sun.security.x509 does not exist
I used java 11 to compile the project.
In my case I had to disable Use '--release' option for cross-compilation
in Java Compiler settings.
This is not an intellij issue.
You need to compile with the -XDignore.symbol.file
option. Some internal packages
are hidden by default unless you add this option to javac.
https://bugs.openjdk.java.net/browse/JDK-7141442
sun.security.x509.CertAndKeyGen and sun.security.pkcs.PKCS10 - missing in JDK8. Implementation suggestions
Also the comment of user @user180100 is relevant and important.
The sun.* packages are not part of the supported, public interface.
A Java program that directly calls into sun.* packages is not guaranteed to work on all Java-compatible platforms. In fact, such a program is not guaranteed to work even in future versions on the same platform.