#fixed code
                                public void addSendJob(Frame f, int sec, int usec) {
        StringBuilder sb = new StringBuilder(40);
        sb.append("< add ");
        sb.append(Integer.toString(sec));
        sb.append(' ');
        sb.append(Integer.toString(usec));
        sb.append(' ');
        sb.append(Integer.toHexString(f.getIdentifier()));
        sb.append(' ');
        sb.append(Integer.toString(f.getLength()));
        sb.append(' ');
        sb.append(Util.byteArrayToHexString(f.getData()));
        sb.append(" >");
        send(sb.toString());
    }
#vulnerable code 
                                public void addSendJob(Frame f, int sec, int usec) {
        synchronized(output) {
            output.print("< add "
                    + Integer.toString(sec) + " "
                    + Integer.toString(usec) + " "
                    + Integer.toHexString(f.getIdentifier()) + " "
                    + Integer.toString(f.getLength()) + " "
                    + Util.byteArrayToHexString(f.getData()) + " >");
            output.flush();
        }
    } 
                            #location 2 
                            #vulnerability type THREAD_SAFETY_VIOLATION