2D Array Declaration, Allocation and Initialization

Declaration

Two-dimensional arrays are objects. A variable such as gradeTable is a reference to a 2D array object. The declaration

int[][] myArray ;


says that myArray is expected to hold a reference to a 2D array of int. Without any further initialization,  it starts out holding null. 
 
Allocation
The declaration 

int[][] myArray = new int[3][5] ;

says that myArray can hold a reference to a 2D array of int, creates an array object of 3 rows and 5 columns, and puts the reference in myArray. All the cells of the array are initialized to zero. The declaration

int[][] myArray = { 
        {0,0,0,0,0}, 
        {0,0,0,0,0}, 
        {0,0,0,0,0} 
    };

does exactly the same thing as the previous declaration (and would not ordinarily be used.)

Initialization

The declaration

int[][] myArray = { 
        {8,1,2,2,9}, 
        {1,9,4,0,3}, 
        {0,3,0,0,7} 
    };

creates an array of the same dimensions (same number of rows and columns) as the previous array and initializes the cells to specific values.