为什么我从主类中收到index = 0和lenght = 0的错误？

我懂了

线程“主”中的异常java.lang.ArrayIndexOutOfBoundsException：在RecursiveSquares.main（RecursiveSquares.java:40）处，索引0超出长度0的范围

public static void draw(int n, double x, double y, double size) {
        if (n == 0) return;

        drawSquare( x, y, size);

        // 2.2 ratio looks good
        double ratio = 2.2;

        // recursively draw 4 smaller trees of order n-1
        draw(n-1, x - size/2, y - size/2, size/ratio);    // lower left  
        draw(n-1, x - size/2, y + size/2, size/ratio);    // upper left  
        draw(n-1, x + size/2, y - size/2, size/ratio);    // lower right 
        draw(n-1, x + size/2, y + size/2, size/ratio);    // upper right
    }


    // read in an integer command-line argument n and plot an order n recursive
    // squares pattern
    public static void main(String[] args) {
        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);