XMLEncoder dont write file properly

Question

I have a method that should write object to XML file

public void save(OutputStream os) {
    XMLEncoder e = new XMLEncoder(new BufferedOutputStream(os));
    e.writeObject(this);
    e.flush();
    e.close();
}

This class have 4 fields

final static public String EOL = System.getProperty("line.separator");
final public static String DEF_FILE_NAME = "security.conf";
private Map<String, String> users = new HashMap<>();
private String logKey;

and many methods, one of methods is save(OutputStream os) presented above.

But XMLEncoder write only this

<?xml version="1.0" encoding="UTF-8"?>
<java version="1.7.0_80" class="java.beans.XMLDecoder">
</java>

What can be wrong?

Answer 1

I have solved it. Problem was in constructor. Class must have public constructor with no parameters.