为什么空指针啊
public static void main(String[] args) {
int number = 2;
List ex = new ArrayList();
String [][] arr = new String[number][];
for (int j = 0; j < 8; j++) {
if (number > 0) {
for (int i = 0; i < number; i++) {
arr[i][j] = "a";
}
}
}
for(int i = 0;i<arr.length;i++){
for(int j=0;j<arr[i].length;j++){
System.out.println(arr[i]);
}
}
}