问道友这个代码是干什么的

import java.util.*;

class Array

{int m, n;Scanner reader=new Scanner(System.in);int[][] arr;

void inputLen(){System.out.print("Please enter array row and column: ");m=reader.nextInt();n=reader.nextInt();arr=new int[m][n];}

int i, j;

void inputArr()

{System.out.println("Please enter "+m+"*"+n+" array: ");

for(i=0; i<m; i++)

for(j=0; j<n; j++)

arr[i][j]=reader.nextInt();}

void sumColumn()

{int[] colSum=new int[n];

for(j=0; j<n; j++){

for(i=0; i<m; i++)

colSum[j]+=arr[i][j];

System.out.println("Column"+(j+1)+" sum="+colSum[j]);}}}

public class App1

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

Array matrix=new Array();matrix.inputLen();matrix.inputArr();matrix.sumColumn();}

}