Question

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: Index 0 out of bounds for length 0
at Art.main(Art.java:29)

What does this mean/How do I fix this?

1 public class Art {
2 // plot a square, centered on (x, y) of the given side length
3 // with a light gray background and black border
4 public static void drawSquare(double x, double y, double size) {
5 PennDraw.setPenColor(PennDraw.LIGHT_GRAY);
6 PennDraw.filledSquare(x, y, size/2);
7 PennDraw.setPenColor(PennDraw.BLACK);
8 PennDraw.square(x, y, size/2);
9 }
10 // plot an order n recursive squares pattern
11 // centered on (x, y) of the given side length
12 public static void draw(int n, double x, double y, double size) {
13 if (n == 0) return;
14
15 drawSquare(x, y, size);
16
17 // 2.2 ratio looks good
18 double ratio = 2.2;
19
20 // recursively draw 4 smaller trees of order n-1
21 draw(n-1, x - size/2, y - size/2, size/ratio); // lower left
22 draw(n-1, x - size/2, y + size/2, size/ratio); // upper left
23 draw(n-1, x + size/2, y - size/2, size/ratio); // lower right
24 draw(n-1, x + size/2, y + size/2, size/ratio); // upper right
25 }
26 // read in an integer command-line argument n and plot an order n recursive
27 // squares pattern
28 public static void main(String[] args) {
29 int n = Integer.parseInt(args[0]);
30 double x = 0.5, y = 0.5; // center of square
31 double size = 0.5; // side length of square
32 draw(n, x, y, size);
33 }
34
35
36 }
37

Answer 1

This means that your trying access an array which has no elements .in your main function your trying to get element from arg arrays

int n = Integer.parseInt(args[0]);
but args array has no elements as these needs to be passed from the command line

so you need to check length of array

Please replace the main method with below code

public static void main(String[] args) {
if(args.length<1){
System.out.println("Please provide the input from command line");
return;
}
int n = Integer.parseInt(args[0]);
double x = 0.5, y = 0.5; // center of square
double size = 0.5; // side length of square
draw(n, x, y, size);
}

}