与数据报一起发送后从String解析int时发生异常

Question

I'm starting to feel real stupid - and hopefully this question's got a simple answer.

I'm trying to send the coordinates of a Point object over UDP. The sending works great:

public void send(Point p) throws IOException {
        String data = Integer.toString(p.x) + " " + Integer.toString(p.y);
        InetAddress IPAddress = InetAddress.getByName(this.remoteHost);
        byte[] sendData = new byte[1024];
        sendData = data.getBytes();
        DatagramPacket sendPacket = new DatagramPacket(sendData, sendData.length, IPAddress, this.remotePort);
        socket.send(sendPacket);
}

And I can receive the data on the other end:

byte[] receiveData = new byte[1024];
DatagramPacket receivePacket = new DatagramPacket(receiveData, receiveData.length);
this.socket.receive(receivePacket);

As you might see I'm sending the String "XY", for example "329 456". I now need to parse those values to integers, so I can use them on the other end:

String[] parts = data.split(" ");
int x = Integer.parseInt(new String(parts[0]));
int y = Integer.parseInt(new String(parts[1]));

But this gives me a NumberFormatException on the y integer ("For input string: '456'"). Why? Is there anything I'm missing here? I've been thinking about he actual encoding of the characters send - could that be the reason why Integer won't understand the value?

Thank you for any help.

Answer 1

I guess you don't take packet length into account when converting packet data to String .

You should do it as follows:

String data = new String(receivePacket.getData(), 0, receivePacket.getLength());

Also, it would be better to specify character encoding explicitly when sending and receiving the message, to prevent issues when machines have different default encodings:

sendData = data.getBytes("UTF-8");
...
String data = new String(receivePacket.getData(), 0, receivePacket.getLength(), "UTF-8");

Answer 2

您是否以这种方式读取数据？

String data = new String(receivePacket.getData(), 0, receivePacket.getLength());