从Java套接字接收信息时更改ArrayList

我得到了这个错误，我只是无法想象的原因。我有一个接收包的receiver类，其中有一个ArrayList。不，数据包没有ArrayList；这个班有一个。当我收到一个新数据包时，ArrayList会被修改，但在我修改它之前。事实上，在我将数据包中的数据读入对象之前，我正在使用数据。不仅如此，ArrayList还在将数组中的所有对象更改为等效对象，该对象是在以后的指令中从数据创建的

产生奇怪行为的方法：

public void processPackets() {
    byte[] buffer = new byte[1024];
    DatagramPacket packet = new DatagramPacket(buffer, buffer.length);

    try {
        while(true) {
            System.out.println("Start:  " + outBuffer);

            socket.receive(packet);
            System.out.println("Before: " + outBuffer);

            // Find out where the packets are coming from
            if (sendHost == null) {
                sendHost = packet.getAddress();
                sendPort = packet.getPort();
            }

            // Grab the data from the packet
            PacketInfo data = new PacketInfo(packet.getData());
            System.out.println("Found: " + data);

            if (this.packetWithinWindow(data.getSequenceNumber())) {
                outBuffer.add(data);
                System.out.println("After:  " + outBuffer);
            }
            ackThePacket(data);

            if (processData()) {break;}; // Returns true after last packet processed

            System.out.println("End:  " + outBuffer);
        }

    } catch (IOException ioe) {
        System.err.println(ioe);
        System.exit(1);
    }

}

假定Exputfer是一个

ArrayList

和

PacketInfo.toString（）

返回一个序列号和前20个字节的列表，这是一个奇怪行为的示例，然后打印到控制台（在Exputfer开始为空的代码中经过几个周期后）：

---

这让我很困惑，所以非常感谢您的帮助。如果有什么帮助的话，这是用Java 6编译的。

您重复使用相同的字节数组，除非您的

PacketInfo

构造函数（您没有显示）复制数据。啊哈！应该是这样！我总是忘记正则数组也是引用类型，因为它们在很多方面都像原语一样处理。谢谢你！

Start:  []
Before: []
Found: 
2 [-120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120]
After:  [
2 [-120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120]]
End:  [
2 [-120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120]]
Start:  [
2 [-120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120, 8, 0, 2, -120]]
Before: [
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48]]
Found: 
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48]
After:  [
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48], 
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48]]
End:  [
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48], 
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48]]
Start:  [
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48], 
1 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 67, 0, 65, 0, 76, 0, 71, 68, 70, 68, 48]]
Before: [
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
Found: 
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
After:  [
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]
End:  [
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0], 
4 [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]]