grade 0,0: 99
grade 2,4: 96
sum: 116

2D Array 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. 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 elements 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.) 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 elements to specific values.