Method javax.crypto.SealedObject.getObject(Key key, String provider) throws NullPointerException if key paramter is null. Such behavior is not specified and should be documented. Here is an example:
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import javax.crypto.SealedObject;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.Cipher;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.SecretKeySpec;
import java.io.IOException;
import java.io.Serializable;
import java.security.*;

public class C implements Serializable {
    public static void main(String argv[]) throws NoSuchAlgorithmException, NoSuchPaddingException, IOException, IllegalBlockSizeException, InvalidKeyException {
        Cipher c = Cipher.getInstance("DES");
        Key k = new SecretKeySpec(new byte[8], "DES");
        c.init(Cipher.ENCRYPT_MODE, k);
        String providerName = c.getProvider().getName();
        SealedObject so = new SealedObject(new C(), c);
        try {
            so.getObject((Key)null, providerName);
        } catch (ClassNotFoundException e) {
            System.out.println("ClassNotFoundException was thrown");
        } catch (NoSuchProviderException e) {
            System.out.println("NoSuchProviderException was thrown");
        } catch (NullPointerException e) {
            System.out.println("NPE was thrown");
        }


    }
}
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aag@gaff:~/work/bugs/doc> javac C.java;java C
NPE was thrown
###@###.### 2004-12-08 13:36:51 GMT