Question

您能告诉我为什么尝试使用其他方法启动列表时看不到列表吗？下面的方法：

public class CollectionsOperation {
    private  List<Client> bufferedReaderClientLIst = new ArrayList<Client>();
    private  List<Client> emptyBoxForCf = new ArrayList<Client>();
    BufferedReader bf = null;


    private static final String fileName = "Clients.txt";

    public List<Client> bufferedReaderCollection() throws IOException {
        String line;        

        bf = new BufferedReader(new InputStreamReader (new FileInputStream(fileName), "UTF-8"));

        while((line = bf.readLine()) != null) {

               String[] split = line.split(";"); 
               String nameCompany = split[0].substring(2);
               String adress = split[1]; 
               String phoneNumber = split[2]; 
               String emailAdress = split[3];

               Client k = new Client(nameCompany, adress, phoneNumber, emailAdress);
               bufferedReaderClientLIst.add(k); 
        }
        System.out.println(bufferedReaderClientLIst); 

        return bufferedReaderClientLIst;

    }
    public void show() throws IOException {
        CollectionsOperation k = new CollectionsOperation();
        k.bufferedReaderCollection();
        System.out.println(bufferedReaderClientLIst); 
    }

调用方法：

public static void main(String[] args) throws IOException { 
        CollectionsOperation k = new CollectionsOperation();                
        k.show();
}

这就是我得到的结果：

[ MarkCompany';Ilusiana';0982882902';mark@company.com,  CorporationX';Berlin';93983';X@Corporation.com]
[]

为什么第二个列表为空？方法bufferedReaderCollection()返回结果，列表bufferedReaderClientLIst可用于所有方法。怎么了？

Answer 1

在show()中：

public void show() throws IOException {
    CollectionsOperation k = new CollectionsOperation();
    k.bufferedReaderCollection();
    System.out.println(bufferedReaderClientLIst); 
}

您创建另一个CollectionsOperation对象以调用bufferedReaderCollection()。这是不必要的。

但是问题出在您打印bufferedReaderClientList的最后一个打印语句中。这是在打印bufferedReaderClientList实例的this，而不是k。由于您尚未在bufferedReaderCollection上调用this，因此该列表将为空，因此[]将显示在末尾。

使用this代替创建另一个实例：

public void show() throws IOException {
    this.bufferedReaderCollection();
    System.out.println(bufferedReaderClientLIst); 
}

为什么我无法通过其他方法显示列表？

1 个答案: