• 所謂的多維，就是一維中含有一維，延伸到3維、4維....，通通都一樣

   int [][] ary1 = new int[3][4];     // 3 x 4
   System.out.println(ary1.length);
   System.out.println(ary1[0].length);
   
   
   int[][] ary2 = new int[3][];       // 3 x ?
   ary2[0] = new int[2];
   ary2[1] = new int[2];
   ary2[2] = new int[1];
   
   System.out.println(ary2.length);
   System.out.println(ary2[0].length);
   System.out.println(ary2[1]).length;
   System.out.println(ary2[2]).length;
   // 3 x ?
   
 }

}  

跑出:
3
4
3
2
2
1