我正在编写一个简单的客户端，但我总是在以下位置收到 NullPointerException:
while ((input = in.readLine()) != null) {
这是我的代码:
public class ClientTest {
public static String server = "127.0.0.1";
public static int sport = 11111;
public static int cport = 11111;
private static String clientname="";
public static ExecutorService pool = Executors.newCachedThreadPool();
public static BufferedReader in = null;
public static PrintWriter out = null;
public static Socket socket = null;
public ClientTest(){
this.clientname="";
}
public static void main(String[] args) {
try {
socket = new Socket(server, sport);
out = new PrintWriter(socket.getOutputStream(), true);
in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
} catch(IOException e) {
System.out.println("could not create connection:\n" + e);
try {
if(socket != null) socket.close();
} catch(Exception ex) {
ex.printStackTrace();
}
}
pool.execute(new Communicator());
}
public static class Communicator implements Runnable {
@Override
public void run() {
String input = "";
try {
while ((input = in.readLine()) != null) {//here i get the NPException
StringTokenizer tokenizer = new StringTokenizer(input);
tokenizer.nextToken();
if(input.startsWith("!open")) {
if(tokenizer.hasMoreTokens()) System.out.print(tokenizer.nextToken() + "> ");
else System.out.print("> ");
}
else if(input.startsWith("!exit")) {
System.out.print("Hallo hallo");
}
}
} catch(IOException e) {
System.out.println("An error as occurred while reading from server - \n" + e);
}
}
}
}
为什么我会收到NullPointerException？我仍在初始化字符串输入。
最佳答案
My question is, why do I get the NP Exception, I am still initializing the String input!
如果 in 为 null，您将得到一个 NullPointerException ......这当然有可能。毕竟，如果 main 的第一部分中的任何内容抛出异常，您可以捕获它，将其打印出来......然后继续!因此，如果 socket.getOutputStream() 抛出异常，in 和 out 都将为 null。
寓意:捕获异常并像什么都没发生一样继续很少是一个好主意。
关于java - java客户端中的NullPointer异常？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/12922893/