Java Question
loading ArrayList<String> from java properties file
I'm reading from a properties-file using this method:
public void loadConfigFromFile(String path) {
Properties prop = new Properties();
InputStream input = null;
try {
//input = new FileInputStream("config.properties");
input = new FileInputStream(path);
// load a properties file
prop.load(input);
// .... saved like this:
// emails: [email protected], [email protected], .....
String wordsS = prop.getProperty("keywords");
String emailS = prop.getProperty("emails");
String feedS = prop.getProperty("feeds");
emails = Arrays.asList(emailS.split(",")); //ERROR !!
words = Arrays.asList( wordsS.split(","))); //ERROR !!
feeds = Arrays.asList( feedS.split(",")); //ERROR !!
allXHours = Float.valueOf(prop.getProperty("frequency"));
} catch (IOException ex) {
ex.printStackTrace();
} finally {
if (input != null) {
try {
input.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
the fields to be written are declared as follows:
private ArrayList<String> emails = new ArrayList<>(
Arrays.asList("[email protected]", "[email protected]")
);
private LinkedList<String> words = new LinkedList<>(
Arrays.asList("vuln", "banana", "pizza", "bonanza")
);
private LinkedList<String> feeds = new LinkedList<>(
Arrays.asList("http://www.kb.cert.org/vulfeed",
"https://ics-cert.us-cert.gov/advisories/advisories.xml",
"https://ics-cert.us-cert.gov/alerts/alerts.xml")
);
..so the compiler shows me the following Information, which I don't know how to use:
Incompatible types. Requiredbut 'asList' was inferred toArrayList<String>: no instance(s) of type variable(s) T exist so thatList<T>conforms toList<T>ArrayList<String>
How to circumvent this?
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Answer Source
The problem is the type of the declared variable that you assign to
emails = Arrays.asList(emailS.split(","));.
According to the compilation error, it is declared as ArrayList but Arrays.asList() returns a List.
You cannot assign a List to an ArrayList while you can do the reverse.
Besides Arrays.asList() return an instance of a private class : java.util.Arrays.ArrayList that is not the same that the ArrayList variable that you declare : java.util.ArrayList. So even a downcast to ArrayList would not work and cause a ClassCastException.
Change the declared variable from
ArrayList<String> emails to List<String> emails and do the same thing for two other ArrayList variables.
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