Java Sound API - capturing microphone

This will get you the default one set by your OS.

AudioFormat format = new AudioFormat(8000.0f, 16, 1, true, true);
TargetDataLine microphone = AudioSystem.getTargetDataLine(format);

To select a particular input device (TargetDataLine) it is better to enumerate the mixers and filter the name of the Mixer you want.

 Mixer.Info[] mixerInfos = AudioSystem.getMixerInfo();
 for (Mixer.Info info: mixerInfos){
  Mixer m = AudioSystem.getMixer(info);
  Line.Info[] lineInfos = m.getSourceLineInfo();
  for (Line.Info lineInfo:lineInfos){
   System.out.println (info.getName()+"---"+lineInfo);
   Line line = m.getLine(lineInfo);
   System.out.println("\t-----"+line);
  }
  lineInfos = m.getTargetLineInfo();
  for (Line.Info lineInfo:lineInfos){
   System.out.println (m+"---"+lineInfo);
   Line line = m.getLine(lineInfo);
   System.out.println("\t-----"+line);

  }

 }