I don't know if you are a C programmer or not but there is an
incongruity between C and Java naming in the audio business.  In Java
Ports are used to get controls, like volume and frame etc.  Lines are
used to capture or play audio data.  SourceDataLines play,
TargetDataLines capture.  Mixers are really complicated as they can have
Ports, SDLs and TDLs associated with them but may not.

Below is a simple example that gets audio data from a URL and plays it
by sending it to a SourceDataLine.  See the comments in the source for
details.

Below that is a Sun program to list the ports on your computer.  I'm
sorry it is formatted so poorly but that is the way it is.

import javax.sound.sampled.*;
import java.io.*;
import java.net.*;

public class AudioExample {
    public static void main(String[] args) throws Exception {
        // get all the mixers
        Mixer.Info[] mixInfo = AudioSystem.getMixerInfo();
        System.out.println("Mixers");
        for (int i=0; i<mixInfo.length; i++)
            System.out.println("   " + mixInfo[i].toString());

        // this is just source data, you can use whatever here
        // this file is from JavaSound, it is over 400k so might
        // take a while to download
        URL url = new URL("http://www.knutejohnson.com/22-new.aif");
        AudioInputStream ais = AudioSystem.getAudioInputStream(url);

        // format will probably be determined by source as in this case
        AudioFormat af = ais.getFormat();
        System.out.println(af.toString());

        // get a SDL with specified format from specified mixer
        SourceDataLine sdl = AudioSystem.getSourceDataLine(af,mixInfo[0]);

        // open requires the format too
        sdl.open(af);
        // no sound until SDL is started
        sdl.start();

        // read and write
        byte[] buf = new byte[1024];
        int bytesRead;
        while ((bytesRead = ais.read(buf)) != -1)
            sdl.write(buf,0,bytesRead);

        ais.close();

        // empty the buffer
        sdl.drain();
        // stop the line
        sdl.stop();
        // close it cause we're done
        sdl.close();
    }
}

/*
 * Copyright (c) 2003 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Sun grants you ("Licensee") a non-exclusive, royalty free, license to
 use, * modify and redistribute this software in source and binary code
 form, * provided that i) this copyright notice and license appear on all
 copies of * the software; and ii) Licensee does not utilize the software
 in a manner * which is disparaging to Sun. * * This software is provided
 "AS IS," without a warranty of any kind. ALL * EXPRESS OR IMPLIED
 CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING ANY * IMPLIED
 WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR *
 NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN AND ITS LICENSORS SHALL NOT BE
 * LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING,
 MODIFYING * OR DISTRIBUTING THE SOFTWARE OR ITS DERIVATIVES. IN NO EVENT
 WILL SUN OR ITS * LICENSORS BE LIABLE FOR ANY LOST REVENUE, PROFIT OR
 DATA, OR FOR DIRECT, * INDIRECT, SPECIAL, CONSEQUENTIAL, INCIDENTAL OR
 PUNITIVE DAMAGES, HOWEVER * CAUSED AND REGARDLESS OF THE THEORY OF
 LIABILITY, ARISING OUT OF THE USE OF * OR INABILITY TO USE SOFTWARE, EVEN
 IF SUN HAS BEEN ADVISED OF THE * POSSIBILITY OF SUCH DAMAGES. * * This
 software is not designed or intended for use in on-line control of *
 aircraft, air traffic, aircraft navigation or aircraft communications; or
 in * the design, construction, operation or maintenance of any nuclear *
 facility. Licensee represents and warrants that it will not use or *
 redistribute the Software for such purposes. */

import javax.sound.sampled.*;

public class ListPorts {
 public static void main(String[] args) {
  Mixer.Info[] aInfos = AudioSystem.getMixerInfo();
  for (int i = 0; i < aInfos.length; i++) {
   try {
    Mixer mixer = AudioSystem.getMixer(aInfos[i]);
    mixer.open();
    try {
     System.out.println(aInfos[i]);
     printPorts(mixer, mixer.getSourceLineInfo());
     printPorts(mixer, mixer.getTargetLineInfo());
    } finally {
     mixer.close();
    }
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
  if (aInfos.length == 0) {
   System.out.println("[No mixers available]");
  }
  System.exit(0);
 }

 public static void printPorts(Mixer mixer, Line.Info[] infos) {
  for (int i = 0; i<infos.length; i++) {
   try {
    if (infos[i] instanceof Port.Info) {
     Port.Info info = (Port.Info) infos[i];
     System.out.println("  Port "+info);
     Port port = (Port) mixer.getLine(info);
     port.open();
     try {
      printControls(port.getControls());
     } finally {
      port.close();
     }
    }
   } catch (Exception e) {
    e.printStackTrace();
   }
  }
 }

 public static void printControls(Control[] controls) {
  for (int i = 0; i<controls.length; i++) {
   printControl("    ", "Controls["+i+"]: ", controls[i]);
  }
  if (controls.length == 0) {
   System.out.println("    [no controls]");
  }

 }

 static boolean balanceTested = false;

 public static void printControl(String indent, String id, Control
 control) {
  if (control instanceof BooleanControl) {
   BooleanControl ctrl = (BooleanControl) control;
   System.out.println(indent+id+"BooleanControl: "+ctrl);
   //try {
   //    Thread.sleep(500);
   //    ctrl.setValue(!ctrl.getValue());
   //    Thread.sleep(500);
   //    ctrl.setValue(!ctrl.getValue());
   //} catch (Exception e) {}
  }
  else if (control instanceof CompoundControl) {
   CompoundControl ctrl = (CompoundControl) control;
   Control[] ctrls = ctrl.getMemberControls();
   System.out.println(indent+id+"CompoundControl: "+control);
   for (int i=0; i<ctrls.length; i++) {
    printControl(indent+"  ", "MemberControls["+i+"]: ", ctrls[i]);
   }
  }
  else if (control instanceof EnumControl) {
   EnumControl ctrl = (EnumControl) control;
   Object[] values = ctrl.getValues();
   Object value = ctrl.getValue();
   System.out.println(indent+id+"EnumControl: "+control);
   for (int i=0; i<values.length; i++) {
    if (values[i] instanceof Control) {
     printControl(indent+"  ", "Values["+i+"]:"+
      ((values[i]==value)?"*":""), (Control) values[i]);
    } else {
     System.out.println(indent+"  Values["+i+"]:"+
      ((values[i]==value)?"*":"")+values[i]);
    }
   }
  }
  else if (control instanceof FloatControl) {
   FloatControl ctrl = (FloatControl) control;
   System.out.println(indent+id+"FloatControl: "+ctrl);
   //try {
   //    Thread.sleep(500);
   //    float x = ctrl.getValue();
   //    ctrl.setValue((float) (Math.random()*(ctrl.getMaximum() -
   //   ctrl.getMinimum()) + ctrl.getMinimum())); //    Thread.sleep(1000);
   //    ctrl.setValue(x); //} catch (Exception e) {} //if (ctrl.getType() ==
   //   FloatControl.Type.BALANCE && !balanceTested) {
   //    balanceTested = true;
   //    for (float y = -1.0f; y<=1.0f; y+=0.02) { //        ctrl.setValue(y);
   //        System.out.println("  Set to "+y);
   //   System.out.println("     res"+ctrl.getValue()); //    } //}
  } else {
   System.out.println(indent+id+"Control: "+control);
  }
 }
}