Thread: array problem

post some code of the 2d array you attempted and some code of what you have now. It is hard to help you if we do not know how much you have already done.

import java.util.Arrays;
 
public class testing
{
    public static void main (String[] args)
    {
        int[] list1 = {5, 8, 3};
        int[] list2 = {2, 99};
        int[] list3 = {5, 3, 7, 3, 3, 66, 88};
        int[] list4 = {2, 4};
        int[] list5 = {2, 5, 7, 3};
 
        int[] listN = new int [list1.length + list2.length + list3.length + list4.length + list5.length];
 
        for ( int i = 0; i < list1.length; i++)
        {
            listN [i] = list1 [i];
        }
        for ( int i = 0; i < list2.length; i++)
        {
            listN [list1.length + i] = list2 [i];
        }
        for ( int i = 0; i < list3.length; i++)
        {
            listN [list1.length + list2.length + i] = list3 [i];
        }
        for ( int i = 0; i < list4.length; i++)
        {
            listN [list1.length + list2.length + list3.length + i] = list4 [i];
        }
        for ( int i = 0; i < list5.length; i++)
        {
            listN [list1.length + list2.length + list3.length + list4.length + i] = list5 [i];
        }
 
        Arrays.sort(listN);
        System.out.println(Arrays.toString(listN));
    }
}

this was when i first tested to prove my logic, and it worked

and this is when i want it as i mentioned above

import java.util.*;
import java.io.*;
import java.util.Arrays;
 
public class Problem3
{
    public static void createArrays (String[] filename) throws FileNotFoundException
    {
         Scanner input = new Scanner (new File (filename[0]));
 
         int N = input.nextInt();
         int arrays [][] = new int [N][];
 
         for ( int i = 0; i < N; i++)
         {
             arrays [N][i] = new []
             input.nextLine();
         }
    }
}

now as you can see inside the for loop i want the length to be read from the file that i will specify in the parameter

"arrays [N][i] = new []" i tried to out "input.nextInt()" inside the two empty brackets here but it didnt work, i figured it it did work, i would have it inside and then write "input.nextLine()" to go on to the next line and take the int again and create the length of the second array

hope this helps

When you want to initialize an array with values, you must use this syntax:

int[] myArray = new int[] {1, 2, 3}; // initialize a length 3 array with values 1, 2, 3

However, if you're reading the values from a file, it's better to initialize the array to all 0 and the correct length because you have no idea what those values may be.

// somehow you got an int variable called length from the file. I suggest using a Scanner object.
int[] myArray = new int[length];

Then you can populate the array with the indexing method.

myArray[0] = 1; // obviously you would replace 1 with a value you read from the array
myArray[myArray.length - 1] = 2; // the last element in the array