When an EC curve is supported by the JDK but not by the underlying native code implementation then a ProviderException is thrown when keypair generation is attempted.

It would be more helpful if the native code implementation could be queried to confirm that the EC curve is actually supported, ahead of keypair generation.

$java UnsupportedCurve
Registered a JCE provider: SunPKCS11-NSS
Exception in thread "main" java.security.ProviderException: sun.security.pkcs11.wrapper.PKCS11Exception: CKR_BUFFER_TOO_SMALL
at jdk.crypto.pkcs11/sun.security.pkcs11.P11KeyPairGenerator.generateKeyPair(P11KeyPairGenerator.java:424)
at java.base/java.security.KeyPairGenerator$Delegate.generateKeyPair(KeyPairGenerator.java:715)
at InvalidCurve.main(InvalidCurve.java:62)
Caused by: sun.security.pkcs11.wrapper.PKCS11Exception: CKR_BUFFER_TOO_SMALL
at jdk.crypto.pkcs11/sun.security.pkcs11.wrapper.PKCS11.C_GenerateKeyPair(Native Method)
at jdk.crypto.pkcs11/sun.security.pkcs11.P11KeyPairGenerator.generateKeyPair(P11KeyPairGenerator.java:416)
... 2 more