non-recursive hanoi tower solver with 3 rods "n" disks in Java

Hanoi.java

public class Hanoi {

	/*
	 * @param int - number of disks
	 */
	static void solve ( int n ) {
		// create the rods
		IntStack rod_A = new IntStack(n);
		IntStack rod_B = new IntStack(n);
		IntStack rod_C = new IntStack(n);

		// push the disks to the start rod
		for ( int i = n; i > 0; i-- ) {
			rod_A.push(i);
		}

		// when there is only one disk
		if ( n == 1 ) {
			// move disk from rod A to C
			rod_C.push(rod_A.pop());
			System.out.println( "  from A to C" );
			// we are done
			return;
		}

		// smallest disk was moved
		boolean small_disk_moved = false;
		// location of smallest disk
		IntStack small_disk_rod = null;
		// last location of smallest disk
		IntStack small_disk_last_rod = null;
		// in case can be divided by 2
		if ( n % 2 == 0 ) {
			small_disk_rod = rod_B;
			rod_B.push(rod_A.pop());
			System.out.println( "  from A to B" );
		} else {
			small_disk_rod = rod_C;
			rod_C.push(rod_A.pop());
			System.out.println( "  from A to C" );
		}

		// info about smallest disk
		small_disk_moved = true;
		small_disk_last_rod = rod_A;

		// start the solving loop
		while ( true ) {
			// if smallest has already moved
			if ( small_disk_moved ) {
				// move the next disk, only one legal move
				if ( small_disk_rod == rod_A ) {
					int disk1 = rod_B.pop();
					int disk2 = rod_C.pop();

					// move to the valid location
					if ( disk1 == -1 && disk2 == -1 ) {
						// no more disks, we are done!
						break;
					} else if ( disk1 == -1 && disk2 != -1 ) {
						rod_B.push(disk2);
						System.out.println( "  from C to B" );
					} else if ( disk1 != -1 && disk2 == -1 ) {
						rod_C.push(disk1);
						System.out.println( "  from B to C" );
					} else if ( disk1 > disk2 ) {
						rod_B.push(disk1);
						rod_B.push(disk2);
						System.out.println( "  from C to B" );
					} else {
						rod_C.push(disk2);
						rod_C.push(disk1);
						System.out.println( "  from B to C" );
					}
				} else if ( small_disk_rod == rod_B ) {
					int disk1 = rod_A.pop();
					int disk2 = rod_C.pop();

					// move to the valid location
					if ( disk1 == -1 && disk2 == -1 ) {
						// no more disks, we are done!
						break;
					} else if ( disk1 == -1 && disk2 != -1 ) {
						rod_A.push(disk2);
						System.out.println( "  from C to A" );
					} else if ( disk1 != -1 && disk2 == -1 ) {
						rod_C.push(disk1);
						System.out.println( "  from A to C" );
					} else if ( disk1 > disk2 ) {
						rod_A.push(disk1);
						rod_A.push(disk2);
						System.out.println( "  from C to A" );
					} else {
						rod_C.push(disk2);
						rod_C.push(disk1);
						System.out.println( "  from A to C" );
					}
				} else {
					int disk1 = rod_A.pop();
					int disk2 = rod_B.pop();

					// move to the valid location
					if ( disk1 == -1 && disk2 == -1 ) {
						// no more disks, we are done!
						break;
					} else if ( disk1 == -1 && disk2 != -1 ) {
						rod_A.push(disk2);
						System.out.println( "  from B to A" );
					} else if ( disk1 != -1 && disk2 == -1 ) {
						rod_B.push(disk1);
						System.out.println( "  from A to B" );
					} else if ( disk1 > disk2 ) {
						rod_A.push(disk1);
						rod_A.push(disk2);
						System.out.println( "  from B to A" );
					} else {
						rod_B.push(disk2);
						rod_B.push(disk1);
						System.out.println( "  from A to B" );
					}
				}
				small_disk_moved = false;
			} else {
				// move the smallest disk to the location it was not previously
				if ( small_disk_rod == rod_A && small_disk_last_rod == rod_B ) {
					small_disk_rod = rod_C;
					small_disk_last_rod = rod_A;
					rod_C.push(rod_A.pop());
					System.out.println( "  from A to C" );
				} else if ( small_disk_rod == rod_A && small_disk_last_rod == rod_C ) {
					small_disk_rod = rod_B;
					small_disk_last_rod = rod_A;
					rod_B.push(rod_A.pop());
					System.out.println( "  from A to B" );
				} else if ( small_disk_rod == rod_B && small_disk_last_rod == rod_A ) {
					small_disk_rod = rod_C;
					small_disk_last_rod = rod_B;
					rod_C.push(rod_B.pop());
					System.out.println( "  from B to C" );
				} else if ( small_disk_rod == rod_B && small_disk_last_rod == rod_C ) {
					small_disk_rod = rod_A;
					small_disk_last_rod = rod_B;
					rod_A.push(rod_B.pop());
					System.out.println( "  from B to A" );
				} else if ( small_disk_rod == rod_C && small_disk_last_rod == rod_A ) {
					small_disk_rod = rod_B;
					small_disk_last_rod = rod_C;
					rod_B.push(rod_C.pop());
					System.out.println( "  from C to B" );
				} else if ( small_disk_rod == rod_C && small_disk_last_rod == rod_B ) {
					small_disk_rod = rod_A;
					small_disk_last_rod = rod_C;
					rod_A.push(rod_C.pop());
					System.out.println( "  from C to A" );
				}
				small_disk_moved = true;
			}
		}
	}

	public static void main ( String argv[] ) {
		int n;

		System.out.print( "Number of disks: " );
		n = Keyboard.readInt();
		if ( n > 0 ) {
			System.out.println( "Disk moves: " );
			solve( n );
		} else {
			System.out.println( "Not a positive number" );
		}
	}
}