How to make sure stdout and stderr is caught from runtimeexec

public class RuntimeExec {

    public RuntimeExec() {
    }

    /**
     * Executes a command
     * @param command
     * @return The result of the command
     * @throws IOException
     */
    public String exec(String command) throws IOException {
     int exitValue = 0;//0 - executed ok.
     String stdOut = null;
     String stdErr = null;
     String result = null;//result from clearcase operation
     StringBuffer out = new StringBuffer();
     StringBuffer err = new StringBuffer();
     Process process = Runtime.getRuntime().exec(command);
     StreamConverter outSc = new StreamConverter(process.getInputStream(),out);
     StreamConverter errSc = new StreamConverter(process.getErrorStream(),err);
        Thread outThread = new Thread(outSc);
        Thread errThread = new Thread(errSc);
        outThread.start();
        errThread.start();
        //Wait until the prosess finish

        long delayMillis = 5000; // 5 seconds
        try {
         //wait for threads to die.
         outThread.join(delayMillis);
            if (outThread.isAlive()) {
                // Timeout occurred; thread has not finished
            } else {
                // Finished
            }
        } catch (InterruptedException e) {
            // Thread was interrupted
        }

      return result;

    }

     // bridge between byte and character stream.
    class StreamConverter implements Runnable {
        private InputStreamReader isr = null;
        private StringBuffer sb = null;
        // end of steam
        private static final int EOS = -1;

        public StreamConverter(InputStream is, StringBuffer sb) {
            isr = new InputStreamReader(is);
            this.sb = sb;
        }

        public void run() {
            int character = 0;
            try{
                while ((character = isr.read()) != EOS) {
                    sb.append((char)character);
                }
            }catch(IOException ioe){
                System.out.println("Could not read std out!"+ioe.getMessage());
            }
        }

    }

    
}