why are you using extra space for array ? I am doing the same without using extra space

int max = Integer.MIN_VALUE,sum=0; for(int i=0;i<4;i++){

        for(int j=0;j<4;j++){

            sum = arr[i][j]+arr[i][j+1]+arr[i][j+2]
                           +arr[i+1][j+1]+
                  arr[i+2][j]+arr[i+2][j+1]+arr[i+2][j+2];
           if(sum>max){
               max=sum;
           }        
        }
    }

    System.out.println(max);