I need to get the length of a 2D array for both the row and column. I’ve successfully done this, using the following code:

public class MyClass 

 public static void main(String args)
 
 int test; 
 test = new int[5][10];

 int row = test.length;
 int col = test[0].length;

 System.out.println(row);
 System.out.println(col);
 

This prints out 5, 10 as expected.

Now take a look at this line:

 int col = test[0].length;

Notice that I actually have to reference a particular row, in order to get the column length. To me, this seems incredibly ugly. Additionally, if the array was defined as:

test = new int[0][10];

Then the code would fail when trying to get the length. Is there a different (more intelligent) way to do this?

Consider

public static void main(String args) 

 int foo = new int 
 new int 1, 2, 3 ,
 new int 1, 2, 3, 4,
 ;

 System.out.println(foo.length); //2
 System.out.println(foo[0].length); //3
 System.out.println(foo[1].length); //4

Column lengths differ per row. If you're backing some data by a fixed size 2D array, then provide getters to the fixed values in a wrapper class.

A 2D array is not a rectangular grid. Or maybe better, there is no such thing as a 2D array in Java.

import java.util.Arrays;

public class Main 
 public static void main(String args) 

 int test; 
 test = new int[5];//'2D array'
 for (int i=0;i<test.length;i++)
 test[i] = new int[i];

 System.out.println(Arrays.deepToString(test));

 Object test2; 
 test2 = new Object[5];//array of objects
 for (int i=0;i<test2.length;i++)
 test2[i] = new int[i];//array is a object too

 System.out.println(Arrays.deepToString(test2));
 

Outputs

[, [0], [0, 0], [0, 0, 0], [0, 0, 0, 0]]
[, [0], [0, 0], [0, 0, 0], [0, 0, 0, 0]]

The arrays test and test2 are (more or less) the same.

Java allows you to create "ragged arrays" where each "row" has different lengths. If you know you have a square array, you can use your code modified to protect against an empty array like this:

if (row > 0) col = test[0].length;

There's not a cleaner way at the language level because not all multidimensional arrays are rectangular. Sometimes jagged (differing column lengths) arrays are necessary.

You could easy create your own class to abstract the functionality you need.

If you aren't limited to arrays, then perhaps some of the various collection classes would work as well, like a Multimap.

If you have this array:

String example = "Please!", "Thanks", "Hello!", "Hey", "Hi!",
 "Why?", "Where?", "When?", "Who?", "Yes!";

You can do this:

example.length;

= 2

example[0].length;

= 2

example[1].length;

= 2

example[0][1].length;

= 3

example[1][0].length;

= 4

Try this following program for 2d array in java:

public class ArrayTwo2 
 public static void main(String args) throws IOException,NumberFormatException
 BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
 int a;
 int sum=0;
 a=new int[3][2];
 System.out.println("Enter array with 5 elements");
 for(int i=0;i<a.length;i++)
 
 for(int j=0;j<a[0].length;j++)
 
 a[i][j]=Integer.parseInt(br.readLine());
 
 
 for(int i=0;i<a.length;i++)
 
 for(int j=0;j<a[0].length;j++)
 
 System.out.print(a[i][j]+" ");
 sum=sum+a[i][j];
 
 System.out.println(); 
 //System.out.println("Array Sum: "+sum);
 sum=0;
 
 

import java.util.Arrays;

public class Main 

 public static void main(String args) 
 

 double test = 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000;

 int removeRow = 0, 1, 3, 4, ;

 double newTest = new double[test.length - removeRow.length][test[0].length];

 for (int i = 0, j = 0, k = 0; i < test.length; i++) 
 if (j < removeRow.length) 
 if (i == removeRow[j][0]) 
 j++;
 continue;
 
 
 newTest[k][0] = test[i][0];
 k++;
 

 System.out.println(Arrays.deepToString(newTest));