java怎么从for语句中获取返回值,我第一个方法中返回了lines可是 打印的时候只打印了[]

package hotel1;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;

import hotel.CloseStreamMethod;

public class ImportData{
public static ArrayList roomsLists = new ArrayList();

public static void main(String[] args) {
    ImportData ip = new ImportData();
    ip.importRooms();



}


public String importData(){

    File src  = new File("/Users/handsomeboy/eclipse-workspace/Coursework/src/hotel1/rooms.txt");

    BufferedReader br = null;

    String lines = null;
    try {
        br = new BufferedReader(new FileReader(src));
        String line = null;
        while((line = br.readLine()) != null) {
            lines += line;
        }

    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        CloseStreamMethod csm = new CloseStreamMethod();
        csm.close(br);
    }
    return lines;
}
public void importRooms() {

    String[] content = importData().split("\n");
    for (String row : content) {
        String[] contents = row.split(",");
          if (contents.length==5) {
            roomsLists.add(new Rooms(Integer.parseInt(contents[0]),
                    RoomType.valueOf(contents[1].toUpperCase()),
                    Double.parseDouble(contents[2]),Integer.parseInt(contents[3]),contents[4]));
          }
        }
    System.out.println(roomsLists);
}

}