java - 无法将数据输入到数据输出流

Question

我正在创建一个程序，该程序从文件中读取，然后将其更改为项目的数组列表并将其发送到客户端。客户通过 ID 选择商品并输入所需金额。然后它会在服务器中更新。服务器运行多线程。当另一个客户端调用服务器时，更新的金额将提供给客户端。

我的客户端代码有问题。发生的情况是我无法输入 id 和 amt，因为程序在我输入值之前关闭。

public class ListClient {

public static void main(String[] args) throws ClassNotFoundException, IOException {

    ObjectOutputStream oos = null;
    ObjectInputStream ois = null;
    try {
        int id = 0;
        int amt = 0;
        Socket s1 = new Socket("localhost", 2001);
        ois = new ObjectInputStream((s1.getInputStream()));

        System.out.println("Connected to test server");
        ListFacade2 lf = new ListFacade2();

        List<Item> lm = (ArrayList<Item>) ois.readObject();
        lf.setItemList(lm);
       Item it = lf.pickItem();
        System.out.println("Item " + it.getId() + " Amount " + it.getQty_left());
        if(it.getQty_left()>0){
        try (DataOutputStream dos = new DataOutputStream(s1.getOutputStream())) {
            System.out.println("Enter the item id that you want:\n");
            dos.writeInt(id);
            System.out.println("Enter the amount of item that you want:\n");
            dos.writeInt(amt);
            dos.flush();
        }}
        else 
            System.out.println("Item out of stock");
    } finally {
        try {
            if (ois != null) {
                ois.close();
            }
            if (oos != null) {
                oos.close();
            }
        } catch (IOException ex) {
        }
    }
}  // end main
}

这是服务器端的代码

public class ListServer {

public static void main(String[] args) {

    try {
        ServerSocket sSoc1 = new ServerSocket(2001);
        while (true) {
            Socket inSoc1 = sSoc1.accept();
            ListThread lt = new ListThread(inSoc1);
            lt.start();
        }
    } catch (Exception e) {
        System.out.println("Oh Dear! " + e.toString());
    }
}
}

class ListThread extends Thread {

Socket threadSoc1;
ListFacade lf = new ListFacade();

ListThread(Socket inSoc1) throws IOException, ClassNotFoundException {
    threadSoc1 = inSoc1;
    lf.readItemList();
}

@Override
public void run() {
    try {

        ObjectOutputStream oos = new ObjectOutputStream((threadSoc1.getOutputStream()));
        System.out.println("server Soc1ket runs");

        oos.writeObject(lf.getListItem());
        DataInputStream dis = new DataInputStream(threadSoc1.getInputStream());
        int id = dis.readInt();
        int amt = dis.readInt();
        lf.updateItem(id, amt);
        lf.displayItem();

    } catch (Exception e) {
        System.out.println("Whoops! " + e.toString());
    }

    try {
        threadSoc1.close();
    } catch (Exception e) {
        System.out.println("Oh no! " + e.toString());
    }
}
}

是因为 pickItem() 返回 null 吗？

public Item pickItem() throws IOException, ClassNotFoundException {
    displayItem();
    System.out.print("Please Key in item id number from above list:  ");
    BufferedReader b = new BufferedReader(new InputStreamReader(System.in));
    Integer itno = Integer.parseInt(b.readLine());
    for(int i = 0; i < im.size();i++){
        if(im.get(i).id.equals(itno))    

            return im.get(i);

        else
            System.out.println("No such item");
    }
    return null;
}

Answer 1

请参阅此处的第一个示例:Scanner

如果您想询问用户输入，您必须从 System.in 中读取(使用扫描仪或类似工具来完成)。

像这样...

Scanner fromUser = new Scanner(System.in);
try (DataOutputStream dos = new DataOutputStream(s1.getOutputStream())) {
        System.out.println("Enter the item id that you want:\n");
        id = fromUser.nextInt();
        dos.writeInt(id);
        System.out.println("Enter the amount of item that you want:\n");
        amt = fromUser.nextInt();
        dos.writeInt(amt);
        dos.flush();
    }

当然，实现同一目标的方法还有很多。这只是一个...