[Demonstration 1]

[Buggy Method]
public BigFraction subtract(final BigFraction fraction) {
    checkNotNull(fraction, "fraction");
    if (fraction.numerator.signum() == 0) {
        return this;
    }
    if (numerator.signum() == 0) {
        return fraction.negate();
    }
    final BigInteger num;
    final BigInteger den;
    if (denominator.equals(fraction.denominator)) {
        num = numerator.subtract(fraction.numerator);
        den = denominator;
    } else {
        num = (numerator.multiply(fraction.denominator)).subtract((fraction.numerator).multiply(denominator));
        den = denominator.multiply(fraction.denominator);
    }
    return new BigFraction(num, den);
}

[Buggy Hunk]
checkNotNull(fraction, "fraction");

[Patch]
checkNotNull(fraction, PARAM_NAME_FRACTION);

[Demonstration 2]

[Buggy Method]
public static void main(String[] args) {
    // configure sinks
    final File stemout = new File(stem);
    final Map<String, String> stemmap = new TreeMap<String, String>();
    // create parser & add add parser callbacks
    EnglishWikiParser wp = new EnglishWikiParser();
    wp.addParser(new EnglishGrammarPageParser(new PageParserCallback() {

        @Override
        public void callback(List<String> left, List<String> right) {
            if (left.size() > right.size()) {
                stemmap.put("\"" + StringUtils.join(left, "\",\"") + "\"", right.get(0));
            }
        }
    }));
    // parse dump
    wp.parse(args[0]);
    // write stems
    try {
        SortedSet<String> keys = new TreeSet<String>(stemmap.keySet());
        FileUtils.writeStringToFile(stemout, "delete from normalization where type='stemming-wiktionary-en';\n");
        for (String key : keys) {
            FileUtils.writeStringToFile(stemout, "insert into normalization (type, origin, normalization, modified_by, modified_at, active) values ('stemming-wiktionary-en', '{" + key + "}','" + stemmap.get(key) + "','TorstenKoester',now(),true);\n", "utf-8", true);
        }
    } catch (IOException e) {
        e.printStackTrace();
    }
}

[Buggy Hunk]
FileUtils.writeStringToFile(stemout, "delete from normalization where type='stemming-wiktionary-en';\n");

[Patch]
FileUtils.writeStringToFile(stemout, "delete from normalization where type='stemming-wiktionary-en';\n", "utf-8");

[Demonstration 3]

[Buggy Method]
public double parseDouble(String num) {
    if (num != null && !num.equals("")) {
        try {
            return Double.parseDouble(num);
        } catch (NumberFormatException e) {
            printError("parseDouble => value => " + num);
        }
    }
    return 0;
}

[Buggy Hunk]
return Double.parseDouble(num);

[Patch]
return Double.parseDouble(num.replaceAll(",", ""));