I need to get all even numbers from random length 2D Array and make another 2D array with even numbe-CodePudding

My Java code get all numbers I need, but every row in new array have length like in old array. How to make array with different row length only for numbers I've got?

Please check for my code:

import java.util.Arrays;
import java.util.Random;

public class Help {
    public static void main(String[] args) {
        Random random = new Random();
        int n = random.nextInt(10);
        int m = random.nextInt(10);
        if (n > 0 && m > 0) {
            int[][] arr = new int[n][m];
            for (int i = 0; i < arr.length; i  ) {
                for (int j = 0; j < arr[i].length; j  ) {
                    arr[i][j] = random.nextInt(20);
                    System.out.print(arr[i][j]   " ");
                }
                System.out.println();
            }
            System.out.println();
            System.out.println("***** EvenMatrix *****");
            int[][] evenMatrix = new int[n][m];
            int evenElement = 0;
            for (int i = 0; i < arr.length; i  ) {
                for (int j = 0; j < arr[i].length; j  ) {
                    if (arr[i][j] % 2 != 0) {
                        continue;
                    } else
                        evenElement = arr[i][j];
                    for (int k = 0; k < arr[i].length; k  ) {
                        evenMatrix[i][j] = evenElement;
                    }
                    System.out.print(evenMatrix[i][j]   " ");
                }
                System.out.println();

            }
            System.out.println(Arrays.deepToString(evenMatrix));

        } else {
            System.out.println("Incorrect array length! Try again!");
            System.exit(0);

        }
    }
}

CodePudding user response：

I wanted to help but didn't understand the question well Let's say your random numbers are 3x3 for n and m

And let's say your array "arr" is

[1,2,3]
[4,5,6]
[7,8,9}

And you want to be your array "evenMatrix" to be

[2,4,6,8] n = 1 and m = 4

  or 

[2,4]  n = 2 and m = 2
[6,8]

Not n = 3 m = 3 just like in the array "arr"

[2,4,6]
[8,0,0]

is that right? If so you can check n and m before creating the "evenArray" like

    int[][] evenMatrix;
    if(n<m)
        evenMatrix = new int[m][m];
    
    else
        evenMatrix = new int[n][n];

creating a square matrix but this still has problems let's say your random numbers are n = 5 and m = 2 so this code will create a 5x5 matrix and fill with even numbers and let's say your randomize arr array doesn't have that many even numbers are so it will become something ugly

CodePudding user response：

The easy solution here is to use an ArrayList, we can easily convert it, note the comments below:

        System.out.println("***** EvenMatrix *****");
        //Create an ArrayList
        ArrayList<ArrayList<Integer>> evenMatrix = new ArrayList<>();
        for (int i = 0; i < arr.length; i  ) {
            //Rather than adding single items, instead create one row at a time
            ArrayList<Integer> evenElementRow = new ArrayList<>();
            for (int j = 0; j < arr[i].length; j  ) {
                if (arr[i][j] % 2 != 0) {
                    continue;
                } else
                    //Add each even number to the evenElementRow
                    evenElementRow.add(arr[i][j]);
                System.out.print(arr[i][j]   " ");
            }
            //Finally at the end of each row we add the complete row to the 3D ArrayList
            evenMatrix.add(evenElementRow);
            System.out.println();

        }
        System.out.println(Arrays.deepToString(evenMatrix.toArray()));

Example output:

19 6 10 19 
16 18 19 16 
13 13 8 10 
8 0 3 10 
14 5 13 3 

***** EvenMatrix *****
6 10 
16 18 16 
8 10 
8 0 10 
14 
[[6, 10], [16, 18, 16], [8, 10], [8, 0, 10], [14]]