Multidimensional arrays in Java are common and can be termed as an array of arrays. Data in a two-dimensional array in Java is stored in 2D tabular form. A two-dimensional array is the simplest form of a multidimensional array. A two-dimensional array can be seen as an array of the one-dimensional array for easier understanding. A two-dimensional array is declared with two dimensions that are also referred to as their bounds.Â
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Syntax of an Array of Arrays:
data_type[][] array_name = new data_type[x][y];
For example: int[][] arr = new int[20][30]; Â Â // 20 X 30 array of arrays
Direct Declaration of an Array of Arrays:
data_type[][] array_name = {
{valueR1C1, valueR1C2, ....},
{valueR2C1, valueR2C2, ....}
};
For example: int[][] arr = {{1, 2}, {3, 4}};
Allocation of values in an Array of Arrays
Java
// Allocation of values in an Array of Arraysclass GFG {Â Â Â Â public static void main(String[] args)Â Â Â Â {Â Â Â Â Â Â Â Â Â Â int[][] arr = new int[20][30];Â Â Â Â Â Â Â Â arr[0][0] = 100;Â Â Â Â Â Â Â Â Â Â System.out.println("arr[0][0] = " + arr[0][0]);Â Â Â Â }} |
arr[0][0] = 100
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Printing complete Array of Arrays
Java
// Printing complete Array of Arraysclass GFG {    public static void main(String[] args)    {          int[][] arr = { { 1, 2 }, { 3, 4 } };          for (int i = 0; i < 2; i++)            for (int j = 0; j < 2; j++)                System.out.println("arr[" + i + "][" + j                                   + "] = " + arr[i][j]);    }} |
arr[0][0] = 1 arr[0][1] = 2 arr[1][0] = 3 arr[1][1] = 4
An array of Arrays in java is actually an array of a one-dimensional array. Each row of a two-dimensional array has a length field that holds the number of columns. However, we can get both the row upper bound and the column dimensions using:
int row_bound = array_name.length; int column_bound = array_name[0].length;
Determine the Dimension of an Array of Arrays
Java
// Determine the Dimension of an Array of Arraysclass GFG {Â Â Â Â public static void main(String args[])Â Â Â Â {Â Â Â Â Â Â Â Â int[][] arr = new int[10][20];Â Â Â Â Â Â Â Â int row_bound = arr.length;Â Â Â Â Â Â Â Â int column_bound = arr[0].length;Â Â Â Â Â Â Â Â System.out.println("Dimension 1: " + row_bound);Â Â Â Â Â Â Â Â System.out.println("Dimension 2: " + column_bound);Â Â Â Â }} |
Dimension 1: 10 Dimension 2: 20
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Note: It is important to understand that Java doesn’t really have two-dimensional arrays. Java arrays are inherently jagged. It has arrays of arrays. So there is no one upper bound/length of the column level.
Example:
Java
// row bound and column boundsclass GFG {    public static void main(String args[])    {        int[][] arr = { { 1, 2 },                        { 3 },                        { 4 },                        { 5, 6, 7, 8 },                        { 9, 10, 11, 12, 13, 14, 15 } };        int row_bound = arr.length;        int column_bound1 = arr[0].length;        int column_bound2 = arr[1].length;        int column_bound5 = arr[4].length;        System.out.println("Dimension 1: " + row_bound);        System.out.println("Dimension 2: " + column_bound1);        System.out.println("Dimension 3: " + column_bound2);        System.out.println("Dimension 4: " + column_bound5);    }} |
Dimension 1: 5 Dimension 2: 2 Dimension 3: 1 Dimension 4: 7
