How to get the private and public key?

Question

there is my code,i want to get the public key and the private key �Cbut i could not find the the approprite method to solve the problem.
import java.security.Key;
import javax.crypto.Cipher;
import java.security.KeyPairGenerator;
import java.security.KeyPair;
import java.security.Security;
public class PublicExample {
public static void main(String[] args) throws Exception {
if (args.length != 1) {
System.err.println("Usage:java PublicExample <text>");
System.exit(1);
byte[] plainText = args[0].getBytes("UTF8");
System.out.println("\nStart generating RSA key");
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("RSA");
keyGen.initialize(512);
KeyPair key = keyGen.generateKeyPair();
System.out.println("Finish generating RSA key");
Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());
Cipher cipher = Cipher.getInstance("RSA/ECB/PKCS1Padding", "BC");
//System.out.println("\n" + cipher.getProvider().getInfo());
System.out.println("\nStart encryption");
cipher.init(Cipher.ENCRYPT_MODE, key.getPublic());
byte[] cipherText = cipher.doFinal(plainText);
System.out.println("Finish encryption:");
System.out.println(new String(cipherText, "UTF8"));
System.out.println("\nStart decryption");
cipher.init(Cipher.DECRYPT_MODE, key.getPrivate());
/*i want to get the private and public key in this method ,but i found the result was not
the one i expected to get,how to solve the problem?
thanks in advance!
System.out.println("private key:" + key.getPrivate().toString());
System.out.println("public key:" + key.getPublic().toString());
byte[] newPlainText = cipher.doFinal(cipherText);
System.out.println("Finish decryption:");
System.out.println(new String(newPlainText, "UTF8"));
thanks in advance!

Answer 1

System.out.println("private key:" +
" + key.getPrivate().toString());
System.out.println("public key:" +
+ key.getPublic().toString());
key.getPrivate() returns an instance of PrivateKey and key.getPublic() returns an instance of PublicKey. Since PublicKey and PrivateKey are interfaces then they will return one of the concrete implementations. Check out the Javadoc for PublicKey and PrivateKey.
When you know which concreate implemenation you have then you can use the methods on that object (by appropriate casting) to find the information you want.