public String getValue(Field field) {
        return getValue(field.getName());
    }
Returns the value defined by this UserCrendentials object for the given
field.

@param field
    The field whose value should be returned.

@return
    The value of the given field, or null if no value is defined for
    that field.
guacamole-ext/src/main/java/org/apache/guacamole/net/auth/credentials/UserCredentials.java