为什么 heroku 会给我这个“不兼容的类型”错误？

Question

我正在尝试在 Heroku.com 上部署我的 discord 机器人，但是我收到一个奇怪的错误... 这是引发错误的类的代码：

package main.Events.lavaplayer;

import com.sedmelluq.discord.lavaplayer.player.AudioPlayer;
import com.sedmelluq.discord.lavaplayer.track.playback.MutableAudioFrame;
import net.dv8tion.jda.api.audio.AudioSendHandler;
import org.jetbrains.annotations.Nullable;

import java.nio.ByteBuffer;

public class AudioPlayerSendHandler implements AudioSendHandler {
    private final AudioPlayer audioPlayer;
    private final ByteBuffer buffer;
    private final MutableAudioFrame frame;

    public AudioPlayerSendHandler(AudioPlayer audioPlayer) {
        this.audioPlayer = audioPlayer;
        this.buffer = ByteBuffer.allocate(1024);
        this.frame = new MutableAudioFrame();
        this.frame.setBuffer(buffer);
    }

    @Override
    public boolean canProvide() {
        return this.audioPlayer.provide(this.frame);
    }

    @Nullable
    @Override
    public ByteBuffer provide20MsAudio() {
        return this.buffer.flip();
    }

    @Override
    public boolean isOpus() {
        return true;
    }
}

这段代码在使用 Intellij 编译时没有给我任何问题，但是当我尝试将它部署到 Heroku 时，他们给了我这个错误：

错误：不兼容的类型：java.nio.Buffer 无法转换为 @org.jetbrains.annotations.Nullable java.nio.ByteBuffer 返回 this.buffer.flip();

Answer 1

flip 返回 Buffer 而不是 ByteBuffer，因此需要强制转换

public ByteBuffer provide20MsAudio() {
    return (ByteBuffer) buffer.flip();
}