这个可以实现行的
import java.util.*;
public class Main{
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
System.out.print("该数组共有几行几列:");
int n=sc.nextInt(); //行
int m=sc.nextInt(); //列
int [][]a=new int[n][m];
int b[]=new int[n];
for (int i = 0; i < n; i++) {
b[i]=0;
for (int j = 0; j < m; j++) {
a[i][j]=sc.nextInt();
if(b[i]<a[i][j]) {
b[i]=a[i][j];
}
}
}
for (int i = 0; i < n; i++) {
System.out.println("第"+(i+1)+"行最大值:"+b[i]);
}
}
}

这个可以实现列:
import java.util.*;
public class Main{
public static void main(String[] args) {
Scanner sc=new Scanner(System.in);
System.out.println("该数组共有几行");
int n=sc.nextInt(); //行
int m=sc.nextInt(); //列
int [][]a=new int[n][m];
int [][]c=new int[n][m];
int b[]=new int[n];
for (int i = 0; i < n; i++) {
for (int j = 0; j < m; j++) {
a[i][j]=sc.nextInt();
c[j][i]=a[i][j];
}
}
for (int i = 0; i < m; i++) {
b[i]=0;
for (int j = 0; j < n; j++) {
if(b[i]<c[i][j]) {
b[i]=c[i][j];
}
}
}
for (int i = 0; i < n; i++) {
System.out.println("第"+(i+1)+"列最大值:"+b[i]);
}
}
}
