使用“if”语句检查后的 NullPointer 异常

问：

我有机器人连接到 IRC 服务器，并且它不会一直崩溃，机器人在机器人的线程“main”java.lang.NullPointerException 中崩溃并出现异常。Report.main（报告.java：47） 47 线是

if (!(str.split(" ")[1].equals("QUIT") || str.split(" ")[1].equals("PART") || str.split(" ")[1].equals("JOIN")))

编辑更多代码

String str = null;    
PrintWriter o;
            Socket s;
            BufferedReader i1;
            s = new Socket("", 6667);
            i1 = new BufferedReader(new InputStreamReader(s.getInputStream()));
            o = new PrintWriter(new OutputStreamWriter(s.getOutputStream()));
            o.print("PASS " + "" + "\r\n");
            o.print("USER " + "" + " 0 * :" + ""
                    + "\r\n" + "NICK " + "" + "\r\n");
            o.print("JOIN " + "#test" + "\r\n");
            o.flush();
    while (s.isConnected()) {
                str = i1.readLine();
                StringBuffer stringBuffer = null;
    if (!(str.split(" ")[1].equals("QUIT") || str.split(" ")[1].equals("PART") || str.split(" ")[1].equals("JOIN"))) {
    ......