```
// "static void main" must be defined in a public class.
public class Main {
private static void printArray(int[][] a) {
for (int i = 0; i < a.length; ++i) {
System.out.println(a[i]);
}
//二维数组行方向的长度
for (int i = 0; i < a.length; ++i) {
//二维数组列方向的长度
for (int j = 0; a[i] != null && j < a[i].length; ++j) {
System.out.print(a[i][j] + " ");
}
System.out.println();
}
}
public static void main(String[] args) {
System.out.println("Example I:");
int[][] a = new int[2][5];
printArray(a);
System.out.println("Example II:");
int[][] b = new int[2][];
printArray(b);
System.out.println("Example III:");
b[0] = new int[3];
b[1] = new int[5];
printArray(b);
}
}
```
