对字符集中字符出现的次数进行排序

import java.util.ArrayList;   
import java.util.Collections;   
import java.util.HashMap;   
import java.util.List;   
import java.util.Map;   
  
/**  
 *  对字符集中字符出现的次数进行排序。 
 */  
public class Test2 {   
	public static void main(String args[]) {   
	    String str = "12345678hfdjkslahfkj932189oiefsjkar94werfdsf";   
	    Map<Character, KeyValue> map = new HashMap<Character, KeyValue>();   
	    char c;   
	    KeyValue kv = null;   
	    for (int i = 0; i < str.length(); i++) {   
			c = str.charAt(i);   
			kv = map.get(c);   
			if (kv == null) {   
				kv = new KeyValue();   
				kv.ch = c;   
				kv.count = 1;   
				map.put(c, kv);   
			} else {   
				kv.count++;   
			}   
	    }   
	    List<KeyValue> list = new ArrayList<KeyValue>(map.values());   
	    Collections.sort(list);   
	    for (KeyValue o : list) {   
	      System.out.println(o.ch + "=" + o.count);   
	    }   
	}   
}   
  
class KeyValue implements Comparable {   

	char ch;	  
	int count;
	
	public int compareTo(Object obj) {   
	    if (obj instanceof KeyValue) {   
	    	KeyValue kv = (KeyValue) obj;   
	    	return kv.count - this.count;   
	    }   
	    return -1;   
	}
}