用 Java 调高/调低计算机音量？

我想用一个命令来调高或调低计算机的主音量（100%/0%）。 我看到我可以使用FloatControl，但我不知道如何使用它。

看看看看使用JavaSound控制主音量 http://www.coderanch.com/t/492931/java/java/Adjusting-master-volume-Windows-XP.

从链接：

Mixer.Info [] mixers = AudioSystem.getMixerInfo();  
System.out.println("There are " + mixers.length + " mixer info objects");  
for (Mixer.Info mixerInfo : mixers)  
{  
    System.out.println("Mixer name: " + mixerInfo.getName());  
    Mixer mixer = AudioSystem.getMixer(mixerInfo);  
    Line.Info [] lineInfos = mixer.getTargetLineInfo(); // target, not source  
    for (Line.Info lineInfo : lineInfos)  
    {  
        System.out.println("  Line.Info: " + lineInfo);  
        Line line = null;  
        boolean opened = true;  
        try  
        {  
            line = mixer.getLine(lineInfo);  
            opened = line.isOpen() || line instanceof Clip;  
            if (!opened)  
            {  
                line.open();  
            }  
            FloatControl volCtrl = (FloatControl)line.getControl(FloatControl.Type.VOLUME);  
            System.out.println("    volCtrl.getValue() = " + volCtrl.getValue());  
        }  
        catch (LineUnavailableException e)  
        {  
            e.printStackTrace();  
        }  
        catch (IllegalArgumentException iaEx)  
        {  
            System.out.println("    " + iaEx);  
        }  
        finally  
        {  
            if (line != null && !opened)  
            {  
                line.close();  
            }  
        }  
    }  
}