code: package org.rosettacode;
  
  import java.util.Collections;
  import java.util.Arrays;
  
  /*
   * recursive backtracking algorithm
   * shamelessly borrowed from the ruby at
   * http://weblog.jamisbuck.org/2010/12/27/maze-generation-recursive-backtracking
   */
  public class MazeGenerator {
  	private final int x;
  	private final int y;
  	private final int[][] maze;
  
  	public MazeGenerator(int x, int y) {
  		this.x = x;
  		this.y = y;
  		maze = new int[this.x][this.y];
  		generateMaze(0, 0);
  	}
  
  	public void display() {
  		for (int i = 0; i < y; i++) {
  			// draw the north edge
  			for (int j = 0; j < x; j++) {
  				System.out.print((maze[j][i] & 1) == 0 ? "+---" : "+   ");
  			}
  			System.out.println("+");
  			// draw the west edge
  			for (int j = 0; j < x; j++) {
  				System.out.print((maze[j][i] & 8) == 0 ? "|   " : "    ");
  			}
  			System.out.println("|");
  		}
  		// draw the bottom line
  		for (int j = 0; j < x; j++) {
  			System.out.print("+---");
  		}
  		System.out.println("+");
  	}
  
  	private void generateMaze(int cx, int cy) {
  		DIR[] dirs = DIR.values();
  		Collections.shuffle(Arrays.asList(dirs));
  		for (DIR dir : dirs) {
  			int nx = cx + dir.dx;
  			int ny = cy + dir.dy;
  			if (between(nx, x) && between(ny, y)
  					&& (maze[nx][ny] == 0)) {
  				maze[cx][cy] |= dir.bit;
  				maze[nx][ny] |= dir.opposite.bit;
  				generateMaze(nx, ny);
  			}
  		}
  	}
  
  	private static boolean between(int v, int upper) {
  		return (v >= 0) && (v < upper);
  	}
  
  	private enum DIR {
  		N(1, 0, -1), S(2, 0, 1), E(4, 1, 0), W(8, -1, 0);
  		private final int bit;
  		private final int dx;
  		private final int dy;
  		private DIR opposite;
  
  		// use the static initializer to resolve forward references
  		static {
  			N.opposite = S;
  			S.opposite = N;
  			E.opposite = W;
  			W.opposite = E;
  		}
  
  		private DIR(int bit, int dx, int dy) {
  			this.bit = bit;
  			this.dx = dx;
  			this.dy = dy;
  		}
  	};
  
  	public static void main(String[] args) {
  		int x = args.length >= 1 ? (Integer.parseInt(args[0])) : 8;
  		int y = args.length == 2 ? (Integer.parseInt(args[1])) : 8;
  		MazeGenerator maze = new MazeGenerator(x, y);
  		maze.display();
  	}
  
  }
  