用户输入到 Java 中的 2 个单独数组

Question

I'm completely new to the Java language. I'm still learning and practicing it but while solving a problem, I got stuck at this. What I want to do is to add 2 elements per line into 2 separate arrays. The first element goes to the X array and the second element goes to the Y array.

public static void main (String[] args) throws IOException {
        BufferedReader reader =new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(reader.readLine());

        double[] X = new double[n];
        double[] Y = new double[n];

        String[] elem = reader.readLine().split(" ");
        for(int i = 0; i < n; i++)
        {

                X[i] = Integer.parseInt(elem[n]);
                Y[i] = Integer.parseInt(elem[n]);

        }

        System.out.println(X, Y);
    }

input:

3 4

1 1

2 3

where the first column is array X and the second column is array Y. I played with code several times but it still gives me "Index 2 out of bounds for length 2".

Answer 1

You have to read your lines inside the for loop. X[i] corresponds to elem[0] ; Y[i] corresponds to elem[1] . For example:

import java.io.*;
import java.util.*;
public class App {
    public static void main(String[] args) throws IOException {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(reader.readLine());

        double[] X = new double[n];
        double[] Y = new double[n];

        for (int i = 0; i < n; i++) {
            String[] elem = reader.readLine().split(" ");
            X[i] = Integer.parseInt(elem[0]);
            Y[i] = Integer.parseInt(elem[1]);
        }
        System.out.println(Arrays.toString(X));
        System.out.println(Arrays.toString(Y));
    }
}

Answer 2

This part is not right:

    for(int i = 0; i < n; i++)
    {
            X[i] = Integer.parseInt(elem[n]);
            Y[i] = Integer.parseInt(elem[n]);

It seems like it should be

    for(int i = 0; (i - 1)< n; i+= 2) // adding two because you are reading two values from elem in every iteration. Changed check to i - 1 to fix case where an odd number of entries will cause an ArrayOutOfBoundsException in elem on i/2 + 1
    {
            X[i/2] = Integer.parseInt(elem[i]);
            Y[i/2] = Integer.parseInt(elem[i] + 1);

(There was a bug in my answer here. It has been fixed)

Alternatively:

for(int i = 0; i < n; i++)
{
  if (i % 2 == 0) X[i/2] = Integer.parseInt(elem[i]);
    else Y[i/2] = Integer.parseInt(elem[i]);