What is legal declaration of array in the following and explain why?and also explain why not others?

Question

int a[][]=new int[4][4];
int[] a[]=new int[4][4];
int a[][]=new int[][4];
int[] a[]=new int[4][];

Answer 1

An OCA question.

All of them are legal except for the third one.

int a[][] = new int[][4];

The dimensions must be created from left to right. The compiler cannot possibly allocate 4 slots of int to an arbitrary number of int[].

int[] a[] is simply equivalent to int[][] a and int a[][].