Implementations of the cryptography classes extend the corresponding base class with implementations of their abstract methods. All data allocation associated with the implementation instance is performed when the instance is constructed. This is done to ensure that any lack of required resources can be flagged when the applet is installed.
Each cryptography class, except KeyPair, has a getInstance method which takes the desired algorithm as one of its parameters. The method returns an instance of the class in the context of the calling applet. Instead of using a getInstance method, KeyPair takes the desired algorithm as a parameter in its constructor.
If you request an algorithm that is not listed in Table 14-1 or that is not implemented in this release, getInstance throws a CryptoException with reason code NO_SUCH_ALGORITHM.