In case of 'getBooleanValue' function, it may raise Null Pointer Exception because of 'equalsIgnoreCase' withtou null check.
```
public boolean getBooleanValue() {
String value = getValue();
if (value.equalsIgnoreCase("y") || value.equalsIgnoreCase("t") ||
value.equalsIgnoreCase("yes") || value.equalsIgnoreCase("true")) {
return true;
} else {
return false;
}
}
```

Therefore, "value" should be checked if null before 'equalsIgnoreCase' to avoid Null Pointer Exception.
It would be better like shown below according to your coding style, I think.
```
public boolean getBooleanValue() {
String value = getValue();
        if (value == null)
            return false;

if (value.equalsIgnoreCase("y") || value.equalsIgnoreCase("t") ||
value.equalsIgnoreCase("yes") || value.equalsIgnoreCase("true")) {
return true;
} else {
return false;
}
}
```