Getting NZEC runtime error while same code is working on IDE

I coded a solution in JAVA(Hotspot 8u112) as provided by codechef IDE,

/* package codechef; // don't place package name! */

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.StringTokenizer;
import java.util.logging.Level;
import java.util.logging.Logger;
import java.lang.* ;

/* Name of the class has to be "Main" only if the class is public. */
class Codechef
{
	static class FastScanner{
        BufferedReader br ;
        StringTokenizer st;

        public FastScanner() {
            br = new BufferedReader(new InputStreamReader(System.in));
        }
        
        String next(){
            while(st==null || !st.hasMoreElements()){
                try {
                    st = new StringTokenizer(br.readLine()) ;
                } catch (IOException ex) {
                    System.out.println("error") ;
                }
            }
            
            return st.nextToken() ;
        }
        
        int nextInt(){
            return Integer.parseInt(next()) ;
        }
    }
    
   public static void main(String args[]){
       
    FastScanner sc = new FastScanner(); 
    
    int T=sc.nextInt() ;
    int n ;
    while(T-->0){
      n = sc.nextInt() ;
      int[] arr = new int[n] ;
      int max=0;
     
      for(int i=0;i<n; ++i){
          arr[i] = sc.nextInt()*20 ;
      }
      for(int i=0;i<n; ++i){
          arr[i]-=(sc.nextInt()*10) ;
          
          max=(max<arr[i])?arr[i]:max ;
      }
      
        System.out.println(max);
       
   }}
}

But, this encounters a RTE, stated as NZEC

Exception in thread "main" java.lang.NullPointerException
	at java.util.StringTokenizer.<init>(StringTokenizer.java:199)
	at java.util.StringTokenizer.<init>(StringTokenizer.java:236)
	at Codechef$FastScanner.next(Main.java:25)
	at Codechef$FastScanner.nextInt(Main.java:35)
	at Codechef.main(Main.java:43)

while the same code runs perfectly on my IDE(NeTbeans 9.0).

Can anyone tell-
a) Why so? What care needs to be taken on codechef.
b) How i can fix it?

You are getting this error because you are not providing inputs.

Click on the check box “Custom Input” and then provide input then it’ll work like a charm ; P

Thanks for quick & clear guidance…:grinning: