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每當我運行我的聊天服務器時，它一直運行到客戶端連接，然後我得到一個空指針例外 connections.add（socket）; 崩潰它，然後每次運行它時都會發生這種情況。 我知道我的客戶端是很好，因爲我在幾個月前看過關於如何做到這一點的教程和服務器與我的客戶工作沒有崩潰Java Socket ArrayList空指針異常
private static ServerSocket server;
private static Socket socket;
private static Scanner input;
private static PrintWriter output;
private static final int port = 444;
private static String message;
private static ArrayList<Socket> connections;
private static Server serverClass;
public Server() {
message = "";
connections = new ArrayList<Socket>();
serverClass = new Server();
}
public void run() {
try {
try {
input = new Scanner(socket.getInputStream());
output = new PrintWriter(socket.getOutputStream());
while(true) {
checkConnection();
if(!input.hasNext()) {
return;
}
message = input.nextLine();
System.out.println("Client said: " + message);
for(int i = 1; i <= connections.size(); i++) {
Socket tempSock = (Socket) connections.get(i - 1);
output.println(message);
output.flush();
}
}
}
finally {
socket.close();
}
}
catch(Exception e) {
System.out.print(e);
}
}
public void checkConnection() throws IOException {
if(!socket.isConnected()) {
for(int i = 1; i <= connections.size(); i++) {
if(connections.get(i) == socket) {
connections.remove(i);
}
}
for(int i = 1; i <= connections.size(); i++) {
Socket disconnectedUser = (Socket) connections.get(i - 1);
System.out.println(disconnectedUser + " has Disconnected!");
}
}
}
public static void main(String[] args) throws IOException{
try {
server = new ServerSocket(port);
System.out.println("Waiting for Clients... ");
while(true) {
socket = server.accept();
connections.add(socket);
System.out.println("Client connected from: " + socket.getLocalAddress().getHostName());
Thread thread = new Thread(serverClass);
thread.start();
}
}
catch(Exception e) {
e.printStackTrace();
}
}
您是否調試過並查看連接中是否有任何值？ – Krishna
@ mdoran3844他正在接受套接字，而不是連接它。除非你錯誤地斷言'ArrayList'不能有空元素，否則你的問題是無關緊要的。 – EJP