package javaphone;

import java.util.ArrayList;
import java.util.HashMap;

/**
 *
 * @author iGroup
 */
public class UserList extends ArrayList<HashMap> {
    private final DataFileIO userDataFile;
    
    public UserList() {
        userDataFile = new DataFileIO("users.xml", "users", "user");
        this.addAll(userDataFile.read());
    }

    public ArrayList getUserData(User user) {
        return null;
    }

    public boolean changeUserData(User user, HashMap userData) {
        return true;
    }

    public String sendUserPassword(int userId) {
        return null;
    }
}

package javaphone;

import java.util.ArrayList;
import java.util.HashMap;

/**
 *
 * @author iGroup
 */
public class UserList extends ArrayList<HashMap> {
    private final DataFileIO userDataFile;
    
    public UserList() {
        userDataFile = new DataFileIO("users.xml", "users", "user");
        this.addAll(userDataFile.read());
    }

    public HashMap getUserData(int userId) {         
        for(HashMap user : this) {
            if(user.containsValue(userId)) {
                return user;
            }
        }
        return null;
    }
}

Update UserList.java