Hanoi program written in Java.

Hanoi.java

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 */
package nj.app;

import java.util.*;
import static java.lang.System.in;
import static java.lang.System.out;

/**
 *
 * @author neojou
 */
public class Hanoi {
    private int num = 0;
    
    class Disk {
        int id = 0;
        Disk(int id) {
            if ( id > 0 )
                this.id = id;
        }
        
        public int getID() {
            return this.id;
        }
        
        public String toString() {
            return String.format("Disk(%d)", this.id);
        }
        
        public int compareTo(Object arg0)  throws ClassCastException{
            Disk obj=(Disk) arg0;
            if(this.id > obj.getID()){return 1;}
            else if(this.id < obj.getID()){return -1;}
            else{return 0;}
        }
    }
    
    class Pole extends ArrayList 
    {
        String name = "";
        
        Pole(String name) {
            this.name = name;
        }
        
        String getName() {
            return this.name;
        }
    }
    
    private Pole pole1 = new Pole("A");
    private Pole pole2 = new Pole("B");
    private Pole pole3 = new Pole("C");
    
    
    Hanoi(int num) {
        if (num > 0 ) {
            this.num = num;
 
            /// create disks and all put at pole1
            
            for (int i=0; i< num; i++) {
                Disk d = new Disk(i+1);
                out.print("set disk: ");
                out.println(d);
                
                pole1.add(d);
                
            }
        }
    }

    void show_status(Pole p) {
        out.printf("%s: %s %n", p.getName(), p);
    }
    
    void show_status() {
        show_status(pole1);
        show_status(pole2);
        show_status(pole3);
    }
    
    void move()
    {
        move_disks(pole1, pole2, pole3, this.num);
    }
    
    void move_disks(Pole p1, Pole p2, Pole p3, int num) {
        if ( num == 1 ) {
            move_disk(p1, p2);
        }
        else {
            move_disks(p1, p3, p2, num-1);
            move_disk(p1, p2);
            move_disks(p3, p2, p1, num-1);
        }
    }
    
    void move_disk(Pole p1, Pole p2) {
            Disk topP1 = (Disk)p1.remove(0);
            out.printf("Move %s from %s to %s %n", topP1, p1.getName(), p2.getName() );
            p2.add(0, topP1);
    }
    
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        
        Scanner console = new Scanner(in);
        out.print("Input Hanoi tower number : ");
        int disk_num = console.nextInt();
        out.printf("%n number = [%d] %n", disk_num);

        Hanoi hanoi = new Hanoi(disk_num);
        hanoi.show_status();

        hanoi.move();

        hanoi.show_status();

    }
    
}