[Demonstration 1]

[Buggy Method]
public boolean isValid(String value) {
    switch(this) {
        case EMAIL:
            {
                return value != null && !value.isEmpty() && !value.contains("@");
            }
        case PASSWORD:
        case USERNAME:
            {
                return value != null && !value.isEmpty();
            }
        default:
            {
                return false;
            }
    }
}

[Buggy Hunk]
return value != null && !value.isEmpty() && !value.contains("@");

[Patch]
return value != null && !value.isEmpty() && value.contains("@");

[Demonstration 2]

[Buggy Method]
@Override
public T apply(int n) {
    if (n < left().size()) {
        return left().apply(n);
    } else if (n > left().size()) {
        return right().apply(size() - left().size() - 1);
    } else {
        return elem;
    }
}

[Buggy Hunk]
return right().apply(size() - left().size() - 1);

[Patch]
return right().apply(n - left().size() - 1);

[Demonstration 3]

[Buggy Method]
private int getProperParam(int value) {
    if (!checkIfNotZero(value))
        return value;
    value -= E;
    return mCurrDeviceType == TABLET ? value *= TABLET_COF : value;
}

[Buggy Hunk]
if (!checkIfNotZero(value)) return value;

[Patch]
if (isEmpty(value)) return value;