这是什么错误
java.security.InvalidKeyException: Diffie-Hellman public key expected
at com.sun.crypto.provider.DHKeyAgreement.engineDoPhase(DHKeyAgreement.java:184)
at javax.crypto.KeyAgreement.doPhase(KeyAgreement.java:567)
at newa.DHdemo.jdkDH(DHdemo.java:47)
at newa.DHdemo.main(DHdemo.java:23)