如何在给定两个密钥的BouncyCastle中获取共享密钥？

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Hex;
import javax.crypto.KeyAgreement;
import java.security.*;
import java.security.spec.X509EncodedKeySpec;

public class SharedKeyExample {
    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());

        // 生成密钥对
        KeyPairGenerator keyPairGenerator = KeyPairGenerator.getInstance("DH");
        keyPairGenerator.initialize(2048);
        KeyPair keyPair = keyPairGenerator.generateKeyPair();

        // 对方的公钥（假设已经获取到）
        String publicKeyString = "公钥字符串";
        byte[] publicKeyBytes = Hex.decode(publicKeyString);

        // 构建对方的公钥对象
        KeyFactory keyFactory = KeyFactory.getInstance("DH");
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec(publicKeyBytes);
        PublicKey publicKey = keyFactory.generatePublic(x509KeySpec);

        // 创建密钥协商对象
        KeyAgreement keyAgreement = KeyAgreement.getInstance("DH");
        keyAgreement.init(keyPair.getPrivate());
        keyAgreement.doPhase(publicKey, true);

        // 计算共享密钥
        byte[] sharedSecret = keyAgreement.generateSecret();

        // 打印共享密钥
        System.out.println("Shared Key: " + Hex.toHexString(sharedSecret));
    }
}