Determine the Upper Bound of a Two Dimensional Array in Java
Last Updated :
26 Oct, 2020
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.
Syntax of an Array of Arrays:
data_type[][] array_name = new data_type[x][y];
For example: int[][] arr = new int[20][30]; // 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
class GFG {
public static void main(String[] args)
{
int [][] arr = new int [ 20 ][ 30 ];
arr[ 0 ][ 0 ] = 100 ;
System.out.println( "arr[0][0] = " + arr[ 0 ][ 0 ]);
}
}
|
Printing complete Array of Arrays
Java
class 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]);
}
}
|
Output
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
class GFG {
public static void main(String args[])
{
int [][] arr = new int [ 10 ][ 20 ];
int row_bound = arr.length;
int column_bound = arr[ 0 ].length;
System.out.println( "Dimension 1: " + row_bound);
System.out.println( "Dimension 2: " + column_bound);
}
}
|
Output
Dimension 1: 10
Dimension 2: 20
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
class 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);
}
}
|
Output
Dimension 1: 5
Dimension 2: 2
Dimension 3: 1
Dimension 4: 7
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