Java Map 키를 기준으로 인스턴스 코드 정렬

package test;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

public  class  Demo  {

  private  HashMap<Integer, Object> map =new HashMap<Integer, Object>();
  private  Set<Integer> keySet = map.keySet();

  public  Object  get(Integer  key)  {
    return  map.get(key);
  }

  public  void  put(Integer  key,  Object  value)  {
    map.put(key,  value);
  }

  @SuppressWarnings("unchecked")
  public void sort()  {
    List<Integer> list =new ArrayList<Integer>(map.keySet());
    Collections.sort(list,  new  Comparator<Object>(){
      public int compare(Object a, Object b) {
         return a.toString().toLowerCase().compareTo(b.toString().toLowerCase());
      }
    });

    this.keySet  =  new  TreeSet<Integer>(list);
  }

  public  Set<Integer>  keySet()  {
    return  this.key
}

  public static void main(String [] args){
    Demo map= new Demo();
    map.put(11, " ");
    map.put(12, " ");
    map.put(13, " ");
    map.put(10, " ");
    map.put(1, " ");
    map.put(8, " ");
    map.put(9, " ");
    map.put(7, " ");
    map.put(5, " ");
    map.put(6, " ");
    map.put(4, " ");
    map.put(3, " ");
    map.put(2, " ");
    System.out.println(" ");
    for (Iterator it =map.keySet().iterator();it.hasNext();){
      Integer key= (Integer)it.next();
      System.out.println( "key[ "  +  key  +  "],  value[ "  +  map.get(key)  +  "] ");
    }
     //
    System.out.println(" ");
     System.out.println( "
 ");
     map.sort();
    for  (Iterator it=map.keySet().iterator();it.hasNext();)  {
      Integer key=(Integer)it.next();
      System.out.println( "key[ "  +  key  +  "],  value[ "  +  map.get(key)  +  "] ");
    }
  } 
}

 
key[ 1],  value[  ] 
key[ 2],  value[  ] 
key[ 3],  value[  ] 
key[ 4],  value[  ] 
key[ 5],  value[  ] 
key[ 6],  value[  ] 
key[ 7],  value[  ] 
key[ 8],  value[  ] 
key[ 9],  value[  ] 
key[ 10],  value[  ] 
key[ 11],  value[  ] 
key[ 12],  value[  ] 
key[ 13],  value[  ] 

 
key[ 1],  value[  ] 
key[ 2],  value[  ] 
key[ 3],  value[  ] 
key[ 4],  value[  ] 
key[ 5],  value[  ] 
key[ 6],  value[  ] 
key[ 7],  value[  ] 
key[ 8],  value[  ] 
key[ 9],  value[  ] 
key[ 10],  value[  ] 
key[ 11],  value[  ] 
key[ 12],  value[  ] 
key[ 13],  value[  ]