Java 如何发现如果文件位于目录中，为什么会引发FileNotFoundException？

这是服务器端代码：

import java.io.FileOutputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.net.ServerSocket;
import java.net.Socket;

public class Server extends Thread {

    public static final int PORT = portno;
    public static final int BUFFER_SIZE = 100;
    ServerSocket serverSocket;

    @Override

    public void run() {
        try {
            serverSocket  = new ServerSocket(PORT);
            while (true) {
                Socket s = serverSocket.accept();
                saveFile(s);
            }
        } 

        catch (Exception e) {
            e.printStackTrace();
        }
    }

    private void saveFile(Socket socket) throws Exception {

        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
        FileOutputStream fos = null;

        byte[] buffer = new byte[BUFFER_SIZE];

        // 1. Read file name.
        Object o = ois.readObject();
        System.out.println("file name is:"+o.toString());
        if (o instanceof String) {
            fos = new FileOutputStream("D://anmolrishte_files//"+o.toString());
        } 
        else {
            throwException("Something is wrong");
        }

        // 2. Read file to the end.
        Integer bytesRead = 0;
        do {
            o = ois.readObject();
            if (!(o instanceof Integer)) {
                throwException("Something is wrong");
            }
            bytesRead = (Integer)o;
            o = ois.readObject();
            if (!(o instanceof byte[])) {
                throwException("Something is wrong");
            }
            buffer = (byte[])o;

            // 3. Write data to output file.
            fos.write(buffer, 0, bytesRead);

        } while (bytesRead == BUFFER_SIZE);

        System.out.println("File transfer success");

        fos.close();
        ois.close();
        oos.close();
    }

    public static void throwException(String message) throws Exception {
        throw new Exception(message);
    }

    public static void main(String[] args) {
        new Server().start();
    }*/

    public static final int PORT = portno;
    public static final int BUFFER_SIZE = 100;
    ServerSocket serverSocket;

    @Override
    public void run() {
        try {
            serverSocket = new ServerSocket(PORT);
            while (true) {
                Socket s = serverSocket.accept();
                saveFile(s); 
            }
        } 

        catch (Exception e) {
            e.printStackTrace();
        }
    }
   private void saveFile(Socket socket) throws Exception {

        ObjectOutputStream oos = new ObjectOutputStream(socket.getOutputStream());
        ObjectInputStream ois = new ObjectInputStream(socket.getInputStream());
        FileOutputStream fos = null;

        byte [] buffer = new byte[BUFFER_SIZE];

        // 1. Read file name.
        Object o = ois.readObject();
        System.out.println("file name is:"+o.toString());
        if (o instanceof String) {    
            System.out.println("hello");
            fos = new FileOutputStream("D://anmolrishte_files//"+o.toString());
            // fos.write(b);
        } 

        else {
            throwException("Something is wrong");
        }

        // 2. Read file to the end.
        Integer bytesRead = 0;

        do {
            o = ois.readObject();

            if (!(o instanceof Integer)) {
                throwException("Something is wrong");
            }

            bytesRead = (Integer)o;
            System.out.println("hello1");
            o = ois.readObject();

            if (!(o instanceof byte[])) {
                throwException("Something is wrong");
            }

            buffer = (byte[])o;

            // 3. Write data to output file.
            fos.write(buffer, 0, bytesRead);

        } while (bytesRead == BUFFER_SIZE);

        System.out.println("File transfer success");

        fos.close();
        ois.close();
        oos.close();
    }

    public static void throwException(String message) throws Exception {
        throw new Exception(message);
    }

    public static void main(String[] args) {
        new Server().start();
    }
}  

这是客户端代码

public class MessageSender extends AsyncTask<Void,Void,Void> {

    File file;
    private static final String ipAddress = "address";
    private static final int port = portno;
    private  Socket socket;

    @Override
    protected Void doInBackground(Void... voids) {
        file = new File(Environment.getExternalStorageDirectory(), "/123.jpg");
        System.out.print(file);

        try {

            socket = new Socket(ipAddress, port);

            ObjectInputStream ois = null;
            ois = new ObjectInputStream(socket.getInputStream());
            ObjectOutputStream oos = null;
            oos = new ObjectOutputStream(socket.getOutputStream());
            oos.writeObject(file.getName());
            FileInputStream fis = null;
            fis = new FileInputStream(file);

            byte[] buffer = new byte[100];
            Integer bytesRead = 0;

            while ((bytesRead = fis.read(buffer)) > 0) {

            }

            oos.writeObject(bytesRead);
            oos.writeObject(Arrays.copyOf(buffer, buffer.length));
            oos.close();
            ois.close();
        } 

        catch (IOException e) {
            e.printStackTrace();
        }

        System.exit(0);
        return null;
    }
}

清单权限是必需的，所以我写了

<uses-permission android:name="android.permission.INTERNET"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

FileNotFoundException发生，但我不知道为什么。此错误在Android Studio中显示：

W/System.err: java.io.FileNotFoundException: /storage/emulated/0/123.jpg (No such file or directory)
    at java.io.FileInputStream.open(Native Method)
    at java.io.FileInputStream.<init>(FileInputStream.java:146)
    at MainActivity$MessageSender.doInBackground(MainActivity.java:167)
    at MainActivity$MessageSender.doInBackground(MainActivity.java:148)
    at android.os.AsyncTask$2.call(AsyncTask.java:305)
    at java.util.concurrent.FutureTask.run(FutureTask.java:237)
    at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:243)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1133)
    at         java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:607)
   04-09 11:06:01.166 4148-4204/W/System.err:     at java.lang.Thread.run(Thread.java:760)

W/System.err:java.io.FileNotFoundException:/storage/emulated/0/123.jpg（没有这样的文件或目录）
在java.io.FileInputStream.open（本机方法）
位于java.io.FileInputStream。（FileInputStream.java:146）
位于MainActivity$MessageSender.doInBackground（MainActivity.java:167）
位于MainActivity$MessageSender.doInBackground（MainActivity.java:148）
位于android.os.AsyncTask$2.call（AsyncTask.java:305）
位于java.util.concurrent.FutureTask.run（FutureTask.java:237）
在android.os.AsyncTask$SerialExecutor$1.run（AsyncTask.java:243）
位于java.util.concurrent.ThreadPoolExecutor.runWorker（ThreadPoolExecutor.java:1133）
位于java.util.concurrent.ThreadPoolExecutor$Worker.run（ThreadPoolExecutor.java:607）
04-09 11:06:01.166 4148-4204/W/System.err:at java.lang.Thread.run（Thread.java:760）

您正在从错误路径读取文件

错误告诉你

没有这样的文件或目录

在这条路上

 /storage/emulated/0/123.jpg

---

因此，只需将您的读取路径更改为正确的路径。

打印您尝试使用的文件的整个路径。您将文件保存在

D://anmolrishte\u files//

中，并尝试从

/storage/emulated/0/

访问它。使用此

环境保存文件。getExternalStorageDirectory（）

。如果我的回答有帮助，请将其标记为已验证以帮助他人。fos=new FileOutputStream（“D://anmolrishte_files/”+o.toString（））；此路径用于将我从客户端收到的文件添加到我的计算机/storage/emulated/0/123.jpg，这是我手机外部目录的路径，其中是save image“123.jpg”，我正在服务器的这条路径上向服务器发送。。。。fos=新文件输出流（“D://anmolrishte_files/”+o.toString（））；您要发送到服务器的图片是您以前使用应用程序拍摄的图片，还是仅仅是现有图片@gouravmanujayeah…此图片存在于我的设备或外部存储器中，我将在单击按钮后直接发送到服务器…从您的设备尝试查找您的图片，查看图片的详细信息，并复制详细信息告诉您的路径@gouravmanujain在我的图片的详细信息中，我可以看到路径是..../storage/FE17-386F/123.jpg…我在…Environment.getExternalStorageDirectory（），“/123.jpg”的位置上也使用了此路径…但它不起作用

 /storage/emulated/0/123.jpg