空指针除

Question

我的代码在eclipse中编译得很好，但是当我在命令提示符下运行它时，我得到一个空指针，第19行除外。null在我的代码中没有用到。请帮助

public class lab4 { 

public static void main(String[] args) throws IOException { 

    InputStreamReader isr = new InputStreamReader (System.in); 
    BufferedReader br = new BufferedReader (isr); 

     ArrayList<String> studentInfo; 
     studentInfo = new ArrayList<String>(); 

     String students = br.readLine();  
     String [] answers = students.split ("\\s+"); 

     while(!students.equalsIgnoreCase("zzzz")){   
      students = br.readLine();               
      studentInfo.add(students); 
     } 

     String [] s0 = studentInfo.get(0).split ("\\s+"); 

这就是问题所在区域它一直指着我：

 while(!students.equalsIgnoreCase("zzzz")){   
      students = br.readLine();               
      studentInfo.add(students); 
     } 

Answer 1

BufferedReader.readLine may return null if the end of the stream has be reached.