Java in a Nutshell, 5th Edition [Electronic resources]

This interface represents an RSA public key and provides direct access to the underlying key values. If you are working with a public key you know is an RSA key, you can cast the PublicKey to an RSAPublicKey.

public interface 
RSAPublicKey  extends java.security.PublicKeyRSAKey {
// Public Constants
5.0   public static final long 
serialVersionUID ;  =-8727434096241101194
// Public Instance Methods
java.math.BigInteger 
getPublicExponent ( );  
}