1

I have this practice Java code that I'm trying to finish. The obvious problem is that when I try to print the array[1][2], it returns null, so I'm thinking the array might be empty. How do I take the user input to put in the array?

import java.util.Scanner;
public class Studyone {


    public static void main(String[] args) 
    {
        Scanner input = new Scanner(System.in);
        int row = 13;
        int col = 25;
        String sentence;
        String sentence2;
        String [][] map = new String[row][col];
        for (int i = 0; i < map.length; i++) 
        {
            for (int j = 0;i < map.length; i++) 
            {
                System.out.println("Enter the element");
                sentence2 = input.nextLine();
                map[i][j]=sentence2;
                if (row>col)
                {
                    break;
                }
            }
        }
        System.out.println(map[1][2]);
    }
}
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5 Answers 5

Reset to default
5

Change

for (int j = 0;i < map.length; i++)

to

for (int j = 0;j < map[0].length; j++)

For example, suppose x = new int[3][4], x[0], x[1], and x[2] are one-dimensional arrays and each contains four elements, as shown in the figure x.length is 3, and x[0].length, x[1].length, and x[2].length are 4

enter image description here

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4 Comments

Fancy pic. I like it. I'd like it even more if arrays x[0], x[1] and x[2] had different lengths, but it's cool already.
@KrzysztofJabłoński are you asking about jagged array?
That's how they're called... Not really asking for another pic, though it's worth emphasizing that inner arrays can have different lengths.
@KrzysztofJabłoński what you want is a jagged array you can look for it on the google
3

This should help, i think:

for (int i = 0; i < map.length; i++) 
{
    for (int j = 0;j < map[i].length; j++) 
    {
        System.out.println("Enter the element");
        sentence2 = input.nextLine();
        map[i][j]=sentence2;
     }
}
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3 Comments

i tried it but the code input just keeps going non-stop
please check your second loop. Do you really use j instead of i?
Yes i checked it, it seems work correctly now. Thanks :)
1

change

for (int j = 0;i < map.length; i++)

to

for (int j = 0;j < map[i].length; j++)
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1 Comment

Shouldn't it be j < map[i].length in the second line and int i = 0 in the first?
1
  • You are incrementing and checking condition for i instead of j in inner loop.
  • Use map[i].length condition for inner loop

So your inner loop should be

for (int j = 0; j < map[i].length; j++)
                ^1      ^2         ^3

As first will increment i twice and for col you have to consider array of one dimension but you are considering map which may lead to ArrayIndexOutOfBoundException.

Here map[i][j]=sentence2; j will remain zero

I changed it, but the input just keeps going on and on non-stop.

It will as you have 13 rows and 25 columns so it will take time to insert all the values.So, just change(reduce) size of array and try.

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1 Comment

i changed it, but the input just keeps going on and on non-stop. @TAsk
0

Amend your code to the following:

for (int j = 0;i < map.length; i++)

to

for (int j = 0;i < map[j].length; j++)
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1 Comment

here i < map[i].length needs to be j < map[i].length

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