写一个java 调用 whisper的代码

首先，需要导入whisper库的依赖，在maven项目中可以在pom.xml中添加如下依赖：

<dependency>
  <groupId>org.whispersystems</groupId>
  <artifactId>whisper-java</artifactId>
  <version>2.2.2</version>
</dependency>

然后就可以在java代码中调用whisper库了。
下面是一个使用whisper进行加密和解密的例子：

import org.whispersystems.libsignal.IdentityKeyPair;
import org.whispersystems.libsignal.SessionBuilder;
import org.whispersystems.libsignal.SessionCipher;
import org.whispersystems.libsignal.SignalProtocolAddress;
import org.whispersystems.libsignal.state.PreKeyBundle;
import org.whispersystems.libsignal.state.PreKeyRecord;
import org.whispersystems.libsignal.state.SignalProtocolStore;
import org.whispersystems.libsignal.util.KeyHelper;

public class WhisperExample {
    public static void main(String[] args) throws Exception {
        //生成自己的IdentityKeyPair
        IdentityKeyPair identityKeyPair = KeyHelper.generateIdentityKeyPair();
        //生成自己的预密钥
        int registrationId = KeyHelper.generateRegistrationId(false);
        PreKeyRecord lastResortPreKey = KeyHelper.generateLastResortPreKey();
        PreKeyRecord preKey = KeyHelper.generatePreKey(22);

        //构建自己的SignalProtocolStore
        SignalProtocolStore signalProtocolStore = new MySignalProtocolStore(identityKeyPair, registrationId, lastResortPreKey, preKey);

        //构建SessionBuilder
        SessionBuilder sessionBuilder = new SessionBuilder(signalProtocolStore, new SignalProtocolAddress("+8613800000000", 1));

        //构建SessionCipher
        SessionCipher sessionCipher = new SessionCipher(signalProtocolStore, new SignalProtocolAddress("+8613800000000", 1));

        //对方的IdentityKey
        IdentityKey theirIdentityKey = new IdentityKey(Base64.decode("H3f0LgRkRlZHVjYXRpb24gLS0gT3BlbkFpIENvcnBvcmF0aW9u"), 0);
        //对方的预密钥
        PreKeyBundle theirPreKey = new PreKeyBundle(1, 22, 328, Base64.decode("H3f0LgRkRl