Two Dimensional arrays

Two-dimensional arrays are defined as "an array of arrays". Since an array type is a first-class Java type, we can have an array of ints, an array of Strings, or an array of Objects. For example, an array of ints will have the type int[]. Similarly we can have int[][], which represents an "array of arrays of ints". Such an array is said to be a two-dimensional array.
The command

int[][] A = new int[3][4];

declares a variable, A, of type int[][], and it initializes that variable to refer to a newly created object. That object is an array of arrays of ints. Here, the notation int[3][4] indicates that there are 3 arrays of ints in the array A, and that there are 4 ints in each of those arrays.
To process a two-dimensional array, we use nested for loops. We already know about for loop. A loop in a loop is called a Nested loop. That means we can run another loop in a loop.

Notice in the following example how the rows are handled as separate objects.

Code: Java
int[][] a2 = new int[10][5];
// print array in rectangular form
for (int i=0; i<a2.length; i++) {
   for (int j=0; j<a2[i].length; j++) {
       System.out.print(" " + a2[i][j]);
   }
   System.out.println("");
}

In this example, "int[][] a2 = new int[10][5];" notation shows a two-dimensional array. It declares a variable a2 of type int[][],and it initializes that variable to refer to a newly created object. The notation int[10][5] indicates that there are 10 arrays of ints in the array a2, and that there are 5 ints in each of those arrays.

Here is the complete code of the example:

public class twoDimension{
 public static void main(String[] args) {
   int[][] a2 = new int[10][5];
   for (int i=0; i<a2.length; i++) {
     for (int j=0; j<a2[i].length; j++) {
       a2[i][j] = i;
       System.out.print(" " + a2[i][j]);
     }
     System.out.println("");
   }
 }
}

Here is the output for the program:

C:\tamana>javac twoDimension.java

C:\tamana>java twoDimension
0 0 0 0 0
1 1 1 1 1
2 2 2 2 2
3 3 3 3 3
4 4 4 4 4
5 5 5 5 5
6 6 6 6 6
7 7 7 7 7
8 8 8 8 8
9 9 9 9 9