int[] array={1,2,3,4,5};
     int[][] array1=new int[][]{{1,2,3},{4,5,6}};
     int[][] array2={{1,2,3},{4,5,6}};
     int[][] array3=new int[2][];
     //array3[0]=new int[4]{1,2,3,4} //wrong!
     array3[0]=new int[]{1,2,3,4};
     //array3[1]={1,2,3};//wrong!