Below is the syntax highlighted version of Htree.java
from §2.3 Recursion.
/************************************************************************* * Compilation: javac Htree.java * Execution: java Htree N * Dependencies: StdDraw.java * * Plot an order N Htree. * * % java Htree 5 * *************************************************************************/ public class Htree { // plot an H, centered on (x, y) of the given side length public static void drawH(double x, double y, double size) { // compute the coordinates of the 4 tips of the H double x0 = x - size/2; double x1 = x + size/2; double y0 = y - size/2; double y1 = y + size/2; // draw the 3 line segments of the H StdDraw.line(x0, y0, x0, y1); // left vertical segment of the H StdDraw.line(x1, y0, x1, y1); // right vertical segment of the H StdDraw.line(x0, y, x1, y); // connect the two vertical segments of the H } // plot an order n H-tree, centered on (x, y) of the given side length public static void draw(int n, double x, double y, double size) { if (n == 0) return; drawH(x, y, size); // compute x- and y-coordinates of the 4 half-size H-trees double x0 = x - size/2; double x1 = x + size/2; double y0 = y - size/2; double y1 = y + size/2; // recursively draw 4 half-size H-trees of order n-1 draw(n-1, x0, y0, size/2); // lower left H-tree draw(n-1, x0, y1, size/2); // upper left H-tree draw(n-1, x1, y0, size/2); // lower right H-tree draw(n-1, x1, y1, size/2); // upper right H-tree } // read in a command line argument N and plot an order N H-tree public static void main(String[] args) { int N = Integer.parseInt(args[0]); draw(N, .5, .5, .5); } }