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I am trying to implement a pause/resume functionality for my audio recording module in Java. So far all I have found on SO is this, which does not give a definitive answer - I have tried the answerer's suggestion of calling start() and stop() on the TargetDataLine to achieve this, and am aware that stop() (from Oracle):

"Stops the line. A stopped line should cease I/O activity. If the line is open and running, however, it should retain the resources required to resume activity. A stopped line should retain any audio data in its buffer instead of discarding it, so that upon resumption the I/O can continue where it left off, if possible."

However I am finding that when I call stop on my TargetDataLine, then sleep for five seconds and call start() to reopen it, the recording never resumes. Here is the code:

import java.io.*;
import java.util.Timer;
import java.util.TimerTask;

import javax.sound.sampled.*;
import javax.sound.sampled.AudioFileFormat.Type;

public class AudioRecorder

 static TargetDataLine targetLine = null;
 static final long maxRecordingTime = 3600000; // One hour in milliseconds
 static Thread recordThread;

 public static void main(String[] args)
 
 try
 
 // Initialise audio format settings and setup data line matching format specification

 initialiseAudioSettings();
 
 catch (LineUnavailableException e)
 
 e.printStackTrace();
 

 // TEST

 startRecording();

 try
 
 System.out.println("Sleeping for 5s...");
 Thread.sleep(5000);
 
 catch (InterruptedException e)
 
 e.printStackTrace();
 

 System.out.println("About to pause recording...");

 pauseRecording();

 try
 
 System.out.println("Sleeping for 5s...");
 Thread.sleep(5000);
 
 catch (InterruptedException e)
 
 e.printStackTrace();
 

 System.out.println("About to resume recording...");

 resumeRecording();

 try
 
 System.out.println("Sleeping for 5s...");
 Thread.sleep(5000);
 
 catch (InterruptedException e)
 
 e.printStackTrace();
 

 System.out.println("About to stop recording...");

 stopRecording();

 System.out.println("Recording stopped...(in theory)");

 // /TEST
 

 private static void initialiseAudioSettings() throws LineUnavailableException
 
 // Define audio format as:
 // Encoding: Linear PCM
 // Sample Rate: 44.1 kHz
 // Bit Depth: 16-bit
 // Channel Format: Stereo
 // Data Storage: Signed & Big-Endian

 final AudioFormat audioFormat = new AudioFormat(44100, 16, 2, true, true);

 // Store format metadata in an Info variable 

 final DataLine.Info audioFormatInfo = new DataLine.Info(TargetDataLine.class, audioFormat);

 if (!AudioSystem.isLineSupported(Port.Info.MICROPHONE))
 
 throw new LineUnavailableException("No microphone has been detected. Please reconnect the microphone and try again.");
 else
 
 System.out.println("Microphone detected. Querying target data line...");
 

 // Use metadata to ascertain whether audio format is supported by default input device

 if (AudioSystem.isLineSupported(audioFormatInfo) == false)
 
 throw new LineUnavailableException("The default input device does not support the specified audio output format");
 

 // Get a line matching the specified audio format 

 targetLine = (TargetDataLine)AudioSystem.getLine(audioFormatInfo);

 // Instruct the system to allocate resources to the targetLine and switch it on

 targetLine.open();

 // Prepare line for audio input

 targetLine.start();
 

 private static void startRecording()
 
 TimerTask scheduleRecordingEnd = new TimerTask()
 
 public void run()
 
 stopRecording();
 
 ;

 Timer recordingTimer = new Timer("Recording Timer");

 recordingTimer.schedule(scheduleRecordingEnd, maxRecordingTime);

 // Setup recording thread

 recordThread = new Thread(new Runnable()
 
 @Override
 public void run()
 
 
 // Route audio input stream to target data line

 AudioInputStream audioInputStream = new AudioInputStream(targetLine);

 // Instantiate output filepath & filename

 File outputFile = new File("C:/temp/test.wav");

 // Write input audio to output .wav file

 try
 
 AudioSystem.write(audioInputStream, AudioFileFormat.Type.WAVE, outputFile);
 
 catch (IOException e)
 
 e.printStackTrace();
 
 
 
 );

 // Start recording

 recordThread.start();
 

 private static void pauseRecording()
 
 targetLine.stop();
 

 private static void resumeRecording()
 
 targetLine.start();
 

 private static void stopRecording()
 
 // Cease all I/O functions of the line

 targetLine.stop();

 // Close the line, deallocating system resources and deleting metadata

 targetLine.close();

 System.out.println("Stopping recording...");

 recordThread.stop();
 

The parts of this code that should be of interest are the tests in main() and the startRecording(), pauseRecording() and resumeRecording() functions, although I have included the code in its entirety for completeness.

Could anyone point me in the right direction as to why this might be happening? Any help would be much appreciated.