[Demonstration 1]

[Buggy Method]
@Override
public String toString() {
    /*length SER IP port file_name hops*/
    String msg = " SER " + ip + " " + port + " " + fileName + " " + hops;
    msg = String.format("%04d", msg.length() + 4) + msg;
    return msg;
}

[Buggy Hunk]
String msg=" SER "+ip+" "+port+" "+fileName+" "+hops;

[Patch]
String msg=" SER "+ip+" "+port+" \""+fileName+"\" "+hops;

[Demonstration 2]

[Buggy Method]
private ArrayList<Object> parseArray(JsonParser jp) throws IOException {
    JsonToken value = jp.nextToken();
    ArrayList<Object> ret = new ArrayList<>();
    while (value != JsonToken.END_ARRAY) {
        if (value == JsonToken.START_OBJECT) {
            Object object = parseObject(jp);
            ret.add(object);
        } else if (value == JsonToken.START_ARRAY) {
            ArrayList<Object> arrayList = parseArray(jp);
            ret.add(arrayList.toArray());
        } else if (value == JsonToken.VALUE_NUMBER_INT) {
            ret.add(jp.getValueAsInt());
        } else if (value == JsonToken.VALUE_FALSE || value == JsonToken.VALUE_TRUE) {
            ret.add(jp.getValueAsBoolean());
        } else if (value == JsonToken.VALUE_NUMBER_FLOAT) {
            ret.add(jp.getValueAsDouble());
        } else if (value == JsonToken.VALUE_STRING) {
            ret.add(jp.getValueAsString());
        } else if (value == JsonToken.VALUE_NULL) {
            ret.add(null);
        }
        value = jp.nextToken();
    }
    return ret;
}

[Buggy Hunk]
ret.add(null);

[Patch]
ret.add("null");

[Demonstration 3]

[Buggy Method]
public static String getFormattedKernelVersion() {
    String procVersionStr;
    try {
        procVersionStr = new BufferedReader(new FileReader(new File("/proc/version"))).readLine();
        String PROC_VERSION_REGEX = "Linux version (\\S+) " + "\\((\\S+?)\\) " + "(?:\\(gcc.+? \\)) " + "(#\\d+) " + "(?:.*?)?" + "((Sun|Mon|Tue|Wed|Thu|Fri|Sat).+)";
        Pattern p = Pattern.compile(PROC_VERSION_REGEX);
        Matcher m = p.matcher(procVersionStr);
        if (!m.matches()) {
            return "Unavailable";
        } else if (m.groupCount() < 4) {
            return "Unavailable";
        } else {
            return new StringBuilder(INSTALLED_KERNEL_VERSION = m.group(1)).append("\n").append(m.group(2)).append(" ").append(m.group(3)).append("\n").append(m.group(4)).toString();
        }
    } catch (IOException e) {
        return "Unavailable";
    }
}

[Buggy Hunk]
return new StringBuilder(INSTALLED_KERNEL_VERSION = m.group(1)).append("\n").append(

[Patch]
return new StringBuilder(Tools.INSTALLED_KERNEL_VERSION = m.group(1)).append("\n").append(