How to scan points in Java

Question

What is the possible way to scan a point in java ? Should I read point.x then point.y or can I read the two co-ordinates at once ?

import java.awt.Point;
import java.util.Scanner;
public class Saleelo {
    public static void main(String[] args) {
        int n = 5;
        Scanner scan = new Scanner(System.in);
        Point[] Points = new Point[60];
        for (int i=0 ; i < n ; i++) {
            Points[i].x = scan.nextInt();
            Points[i].y = scan.nextInt();
            System.out.println(Points[i]);
        }   
    }
}

This what I have tried and it gives me null pointer exception

How do you want the user to enter points? That really answers your first question by definition. The reason you get an NPE is that new never _create_ the `Point` - `Points[i] = new Point()`; and array is initialised to `null`. Also, stick to Java naming conventions, variables should be in `camelCase`. — Boris the Spider, Apr 16 '15 at 16:17
Not surprising. you didn't initialize anything in `Points` so `Points[i].x` is probably throwing your null pointer. — tnw, Apr 16 '15 at 16:18

Reimeus · Answer 1 · 2015-04-16T16:27:42.293

1

Instantiate each array element before attempting to assign values to its elements

for (int i=0 ; i < points.length ; i++) {
    points[i] = new Point();
    ...

where the points array is initialized with just the 5 elements that you will use

edited Apr 16 '15 at 16:27

answered Apr 16 '15 at 16:18

Reimeus

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I would add to this answer that there is no point in creating a `Point[60]` if the length if already fixed to 5. Upvoted. – Jean-François Savard Apr 16 '15 at 16:20
@Jean-François Savard: there is no point in creating the array at all… – Holger Apr 16 '15 at 16:32
@Holger Certainly for a `println` only, but I believe this is a simplified snippet. – Jean-François Savard Apr 16 '15 at 16:33
1

@Jean-François Savard: under the premise that this is a simplified example, there might be a use for the other 55 array entries as well. To add something to the answer, I’d recommend to initialize the value at construction, i.e. `points[i] = new Point(scan.nextInt(), scan.nextInt());` instead of using three statements like `points[i] = new Point(); points[i].x = scan.nextInt(); points[i].y = scan.nextInt();` – Holger Apr 16 '15 at 16:36
@Holger I agree that your addition is better. As for the 55 other entries, I don't really see how they could be used logically if we have an `n` variables which represent the length of input. – Jean-François Savard Apr 16 '15 at 16:46

How to scan points in Java

1 Answers1