Challenge problem

This code is running perfectly in eclipse but here it is showing error can anyone tell me why?

import java.util.*;

public class Main {

static Scanner scn=new Scanner(System.in);
public static void main(String args[]) {
	int[][] arr=null;
	int M=scn.nextInt();
	int N=scn.nextInt();
	if(M>=1&&M<=10&&N>=1&&N<=10) {
		arr=new int[M][N];
	}
	arr=take_input(arr);
	wave_print(arr);
}
public static int[][] take_input(int[][] array){
	for(int i=0;i<array.length;i++) {
		for(int j=0;j<array[i].length;j++) {
			array[i][j]=scn.nextInt();
		}
	}
	return array;
}
public static void wave_print(int[][] arr) {
	int i,j;
	for(i=0;i<arr.length;i++) {
		if(i%2==0) {
			for(j=0;j<arr[i].length;j++) {
				System.out.print(arr[i][j]+",");
			}
		}
		else {
			for(j=arr[i].length-1;j>=0;j--) {
				System.out.print(arr[i][j]+", ");
			}
		}
	}
	System.out.println("END");
}

}