Getting the array length of a 2D array in Java

Question

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 s         


        

Answer 1

public class Array_2D {
int arr[][];
public Array_2D() {
    Random r=new Random(10);
     arr = new int[5][10];
     for(int i=0;i<5;i++)
     {
         for(int j=0;j<10;j++)
         {
             arr[i][j]=(int)r.nextInt(10);
         }
     }
 }
  public void display()
  {
         for(int i=0;i<5;i++)

         {
             for(int j=0;j<10;j++)
             {
                 System.out.print(arr[i][j]+" "); 
             }
             System.out.println("");
         }
   }
     public static void main(String[] args) {
     Array_2D s=new Array_2D();
     s.display();
   }  
  }

Answer 2

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;
        }
    }
}

Answer 3

.length = number of rows / column length

[0].length = number of columns / row length

Answer 4

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.

Answer 5

With Java 8, allow you doing something more elegant like this:

int[][] foo = new int[][] {
        new int[] { 1, 2, 3 },
        new int[] { 1, 2, 3, 4},
    };

int length = Arrays.stream(array).max(Comparator.comparingInt(ArrayUtils::getLength)).get().length

Answer 6

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;