如何用Java改变主音量？

import javax.sound.sampled.*;

public class MainVolumeChanger {
    public static void main(String[] args) {
        try {
            // 获取默认音频设备
            Mixer.Info[] mixerInfos = AudioSystem.getMixerInfo();
            Mixer mixer = AudioSystem.getMixer(mixerInfos[0]);

            // 获取主音量控制器
            Line.Info[] lineInfos = mixer.getTargetLineInfo();
            for (Line.Info lineInfo : lineInfos) {
                Line line = mixer.getLine(lineInfo);
                if (line instanceof Port) {
                    Port port = (Port) line;
                    if (port.isControlSupported(FloatControl.Type.VOLUME)) {
                        FloatControl volumeControl = (FloatControl) port.getControl(FloatControl.Type.VOLUME);

                        // 设置主音量为50%
                        float volume = volumeControl.getMaximum() * 0.5f;
                        volumeControl.setValue(volume);
                    }
                }
            }
        } catch (LineUnavailableException e) {
            e.printStackTrace();
        }
    }
}